This reverts commit 1af2d7ba.

  * Note: breaking change; since this commit, a plugin that has
    worked so far might get rejected due to plugin maturity
  * mariabackup is not affected (allows all plugins)
  * VERSION file defines SERVER_MATURITY, which defines the
    corresponding numeric value as SERVER_MATURITY_LEVEL in
    include/mysql_version.h
  * The default value for 'plugin_maturity' is SERVER_MATURITY_LEVEL - 1
  * Logs a warning if a plugin has maturity lower than
    SERVER_MATURITY_LEVEL
  * Tests suppress the plugin maturity warning
  * Tests use --plugin-maturity=unknown by default so as not to fail
    due to the stricter plugin maturity handling

This commit implements aggregate stored functions. The basic idea behind
the feature is:

* Implement a special instruction FETCH GROUP NEXT ROW that will pause
the execution of the stored function. When the instruction is reached,
execution of the initial query resumes "as if" the function returned.
This gives the server the opportunity to advance to the next row in the
result set.

* Stored aggregates behave like regular aggregate functions. The
implementation of thus resides in the class Item_sum_sp. Because it is
an aggregate function, for each new row in the group, the
Item_sum_sp::add() method will be called. This is when execution resumes
and the function does another iteration to "add" one extra element to
the final result.

* When the end of group is reached, val_xxx() method will be called for
the item. This case is handled by another execute step for the stored
function, only with a special flag to force a call to the return
handler. See Item_sum_sp::execute() for details.

To allow this pause and resume semantic, we must preserve the function
context across executions. This is stored in Item_sp::sp_query_arena only for
aggregate stored functions, but has no impact for regular functions.

We also enforce aggregate functions to include the "FETCH GROUP NEXT ROW"
instruction.
Signed-off-by: Vicențiu Ciorbaru <vicentiu@mariadb.org>

Item_sp::init_result_field no longer takes sp_head* parameter. It
expects the m_sp member to be already set to something valid.

In preparation for implementing custom aggregate functions, refactor
the common code between regular stored functions and aggregate stored
functions. This includes:

* initialising SP result field
* executing a SP
* access checks

In addition, refactor sp_head::execute_function to take two extra
parameters, a function rcontext and a Query_arena. These two paremeters
were initially initialised and destroyed within
sp_head::execute_function, but for aggregate stored functions we will
require control over their lifetime. The owner of these objects now
becomes Item_sp.
Signed-off-by: Vicențiu Ciorbaru <vicentiu@mariadb.org>

Suggested-by: Sergey Vojtovich <svoj@mariadb.org>

Includes Spider patches
- 062_mariadb-10.2.0.direct_join_1and3.diff
- 063_mariadb-10.2.0.direct_join_for_single_partition.diff
- Test cases from Kentoku

Allows Spider to push full joins to the Spider engine trough the
create_group_by interface.

Other things:
- Increased MYSQL_VERSION_ID to check for 10211 (latest 10.2 version)
- Fix for const_table at calling create_group_by().

Original author: Kentoku SHIBA

Signed-off-by: Monty <monty@mariadb.org>

New features in 3.3.13 are:
- Join Push Down for 1 by 1 table and single partition.

Add support for direct update and direct delete requests for spider.
A direct update/delete request handles all qualified rows in a single
operation rather than one row at a time.

Contains Spiral patches:
006_mariadb-10.2.0.direct_update_rows.diff      MDEV-7704
008_mariadb-10.2.0.partition_direct_update.diff MDEV-7706
010_mariadb-10.2.0.direct_update_rows2.diff     MDEV-7708
011_mariadb-10.2.0.aggregate.diff               MDEV-7709
027_mariadb-10.2.0.force_bulk_update.diff       MDEV-7724
061_mariadb-10.2.0.mariadb-10.1.8.diff          MDEV-12870

- The differences compared to the original patches:
  - Most of the parameters of the new functions are unnecessary.  The
    unnecessary parameters have been removed.
  - Changed bit positions for new handler flags upon consideration of
    handler flags not needed by other Spiral patches and handler flags
    merged from MySQL.
  - Added info_push() (Was originally part of bulk access patch)
  - Didn't include code related to handler socket
  - Added HA_CAN_DIRECT_UPDATE_AND_DELETE

Original author: Kentoku SHIBA
First reviewer:  Jacob Mathew
Second reviewer: Michael Widenius

- Ensure that var= doesn't have a space before =
- Fixed DBUG_PRINT to use %u for unsigned types
- Use "enter" when printing function arguments
- Fixed typos
- Added some extra DBUG_PRINT
- Removed not needed assignment

This is about adding more options to force slave retries

Two new variables has been added:
slave_transaction_retry_errors
- Tells the slave thread to retry transaction for replication when a
  query event returns an error from the provided list. Deadlock and
  elapsed lock wait timeout errors are automatically added to this list
slave-transaction-retry-interval
- Interval of the slave SQL thread will retry a transaction
  in case it failed with a deadlock or elapsed lock wait
  timeout or listed in slave_transaction_retry_errors

Other changes:
- Simplifed code for slave_skip_errors (to be aligned with
  slave_transaction_retry_errors)
- Renamed print_slave_skip_errors() to make_slave_skip_errors_printable()
- Remove printing error from init_slave_skip_errors as my_bitmap_init()
  will do that if needed.
- Generalize has_temporary_error()

Spiral Patch 057: 057_mariadb-10.2.0.partition_index_end.diff MDEV-12999

Original author: Kentoku SHIBA
First reviewer:  Jacob Mathew
Second reviewer: Michael Widenius

- In Spider, calling cmp_ref() can be very expensive. In ha_partition.cc
  we don't anymore sort rows according to position for the Spider
  engine.
- Removed Spider specific call info(HA_EXTRA_STARTING_ORDERED_INDEX_SCAN)
  from handle_ordered_index_scan(). It's caused performance issues and
  does not change results for queries with ORDER BY.
- The visible effect of this patch is that for some storage engines,
  rows may be returned in a different order if there is no ORDER BY clause.

- Based in Spiral Patch 052:
  052_mariadb-10.2.0.add_partition_skip_pk_sort_for_non_clustered_index
  MDEV-7748
- The major difference from original patch is that there is no variable to
  get the old behaviour.

Other things:
- Optimized ha_partition::cmp_ref() and cmp_part_ids() to make them
  simpler and faster.
- Changed arguments to cmp_key_part_id() to be same as
  cmp_key_rowid_part_id to simplify code.

Original author: Kentoku SHIBA
First reviewer:  Jacob Mathew
Second reviewer: Michael Widenius

Contains Spiral patches:
022_mariadb-10.2.0.auto_increment.diff               MDEV-7720
030: 030_mariadb-10.2.0.partition_auto_inc_init.diff MDEV-7726

These patches have the following differences compared to the original
patches:
- Added the new #defines for the feature in spd_environ.h instead of in
  handler.h because these #defines are needed by Spider and are not needed
  by the server.
- Cleaned up code related to the removed variable m_need_info_for_auto_inc
. Changed variable assignment in lock_auto_increment() and
  unlock_auto_increment() so that the assignments are done under locks.
- Added a test case.
- Added test result changes resulting from a bug that was fixed by these
  patches.

Original author: Kentoku SHIBA
First reviewer:  Jacob Mathew
Second reviewer: Michael Widenius

Contains Spiral patches:
007_mariadb-10.2.0.partition_fulltext.diff  MDEV-7705
038_mariadb-10.2.0.partition_fulltext2.diff MDEV-7734

This commit has the following differences compared to the original
patches:

- Added necessary full text search cleanup at the storage engine layer
  that was omitted in the original patch.
- Added test case.
- A lot of code cleanups to make the code notable smaller.
- Changed SQL code to use ha_ft_end() instead of ft_end()

Original author: Kentoku SHIBA
First reviewer:  Jacob Mathew
Second reviewer: Michael Widenius

Spider patches 026 (MDEV-7723), 031 (MDEV-7727) and 058 (MDEV-12532)

This allows the storage engine to internally compute sum and count
operations.

- Enhance sum items to be able to store the sum value directly.
- return_record_by_parent() is enabled in spider as
  HANDLER_HAS_DIRECT_AGGREGATE is defined
- Added spd_environ.h to spider. This is loaded first to ensure that all
  MariaDB specific defines that are used by include files are properly
  defined.
- This code is tested by the existing spider tests direct_aggregate.test
  and direct_aggregate_part.test and also partition.test

Done to simplify spider patch for direct aggregates

Other things:
- Cleanup of allocated bitmaps done in open(), which
  simplifies init_partition_bitmaps()
- Add needed defines in ha_spider.cc to enable new spider code
- Fixed some DBUG_PRINT() to be consistent with normal code
- Removed end space
- The changes in test cases partition_innodb, partition_range,
  partition_pruning etc are becasue partitions can now more exactly
  calculate the number of rows in a range.

Contains spider patches:
014,015,023,033,035,037,040,042,044,045,049,050,051,053,059

Allow partition engines to access table->s->connect_string for engines
that uses HTON_CAN_READ_CONNECT_STRING_IN_PARTITION
Don't reset table->s->connect_string in ha_partition::open

Added Spider patches:
003_mariadb-10.0.15.vp.diff
060_mariadb-10.2.0.partition_reset_top_table_fields.diff

- Support HA_EXTRA_ADD_CHILDREN_LIST,HA_EXTRA_ATTACH_CHILDREN,
  HA_EXTRA_IS_ATTACHED_CHILDREN and HA_EXTRA_DETACH_CHILDREN
  in partition handler for handlers that has HA_CAN_MULTISTEPL_MERGE flag
- Added HA_CAN_MULTISTEPL_MERGE to MERGE handler.
- Added handler::get_child_handlers()
- Change m_num_lock to contain total number of locks. This was needed as
  we now adjust number of locks when extra(HA_EXTRA_ATTACH_CHILDREN) is
  called.

- Enable HA_EXTRA_WRITE_CAN_REPLACE and HA_EXTRA_WRITE_CANNOT_REPLACE for
  partition engine.

- Added cond_push() and cond_pop() to ha_partition.cc

013_mariadb-10.0.15.vp_handler.diff
034_mariadb-10.0.15.vp_handler2.diff
005_mariadb-10.0.15.hs.diff
041_mariadb-10.0.15.vp_handler2.diff
+ Fixes from Kentoku
+ Added handler/suite.pm and handler/suite.opt to be able to run test cases
  in spider/handler

Also changed Unique row not found to use uppercase first.
This was done to make these messages consistent with the rest

- mysql_install_db now prints position to error file, if log-error is used
- Warning about compatibility now mentions MySQL 5.6 and 5.7
- Give warning if --show_compatibility_56 is used

This was done to make thing consistent. It gives the additional benefit
that EXPLAIN EXTENDED now treat null_tables like constant's and replaces
columns with NULL, in a similar way that it replaces columns with constants
for constant tables.

- Null tables are tables where all columns are always NULL. The most common
  NULL TABLE is a table used in a LEFT_JOIN that is never true.
- All result changes comes from replacing columns with NULL for null_tables.
- "Impossible where" is now also shows constants for const columns.
- Removed duplicated s->type= JT_CONST
- Reset found_const_table_map when JOIN is created (safety fix)

srv_purge_wakeup(): If thd_destructor_proxy has initiated the first
step of shutdown, ensure that all purge threads terminate.

logs_empty_and_mark_files_at_shutdown(): Add a debug assertion.
(The purge threads should have been shut down already before this step.)

(possibly intermittent) checksum mismatch.

trx_set_rw_mode() is never called for read-only transactions, this is guarded
by callers.

Removing this condition from critical section immediately gives 5% scalability
improvement in OLTP index updates benchmark.