FLUSH TABLES kills all insert delayed treads. If this happens at same time
as a newly started insert delayed query, the insert may fail with either
and error ("Query interrupted") or the row may be lost.
This patch fixes this by changing a failed attempt of get_delay_table() to
convert the query to use a normal insert.

The test case for this patch can be found in the FLUSH TABLES commit after
this one.

Part of MDEV-5336 Implement LOCK FOR BACKUP

The idea is that instead of waiting in close_cached_tables() for all
tables to be closed, we instead call flush_tables() that does:
- Flush not used objects in table cache to free memory
- Collect all tables that are open
- Call HA_EXTRA_FLUSH on the objects, to get them into "closed state"
- Added HA_EXTRA_FLUSH support to archive and CSV
- Added multi-user protection to HA_EXTRA_FLUSH in MyISAM and Aria

The benefit compared to old code is:
- FTWRL doesn't have to wait for long running read operations or
  open HANDLER's

Part of MDEV-5336 Implement LOCK FOR BACKUP

Added support for backup calls in Aria to protect
removal of redo logs.

- The old code used the original create_info from lex, not the new one
  that includes more information (like OPT_OR_REPLACE).
  The bug was not discovered as the code in lock_table_named() only
  checked for OPT_OR_REPLACE in case of timeout errors.
  As lock_table_names will be fixed as part of BACKUP STAGE's, there
  is no changes in lock_table_names() in this commit.
- Removed also the 'temporary' copy of statement flags to thd for
  lock_table_names()

- Moved tests depending on utf8 characters from create to create_utf8
- Fixed some tests in create and sp that wrongly tried to create table
  from non existing table on existing table.  In a later patch we may
  first check if table exists, in which case the error message would
  change.
- Updated results for partition_debug_tokudb

Bascially this means that all builds with BUILD scripts are done with
--with-jemalloc=NO      # Required by tokudb
--with-ssl              # Required on OpenSuse 10.5 to get galera to work

- Remove obsolete documentation files
- Removed old obsolete information from some documentation files

Added to new values to the server variable use_stat_tables.
The values are COMPLEMENTARY_FOR_QUERIES and PREFERABLY_FOR_QUERIES.
Both these values don't allow to collect EITS for queries like
    analyze table t1;
To collect EITS we would need to use the syntax with persistent like
   analyze table t1 persistent for columns (col1,col2...) index (idx1, idx2...) / ALL

Changing the default value from NEVER to PREFERABLY_FOR_QUERIES.

use_stat_tables= PREFERABLY
optimizer_use_condition_selectivity= 4

MDEV-17928 Conversion from TIMESTAMP to VARCHAR SP variables does not work well on fractional digits

Sort acl_users inside the mysql_rename_user()'s loop, after every
successful iteration.

This is needed because on the next loop's iteration find_user_exact()
is used, which requires correct sorting by name.

&sys_buf + DATA_TRX_ID_LEN is not &(sys_buf + DATA_TRX_ID_LEN).

create_table_def(), ha_innobase::create(): Defer fts_optimize_add_table()
until after the table has been successfully created.

row_fts_merge_insert(): Correctly initialize DB_ROLL_PTR to a safe value
that will not be dereferenced by MVCC.

This patch changes how old rows in mysql.gtid_slave_pos* tables are deleted.
Instead of doing it as part of every replicated transaction in
record_gtid(), it is done periodically (every @@gtid_cleanup_batch_size
transaction) in the slave background thread.

This removes the deletion step from the replication process in SQL or worker
threads, which could speed up replication with many small transactions. It
also decreases contention on the global mutex LOCK_slave_state. And it
simplifies the logic, eg. when a replicated transaction fails after having
deleted old rows.

With this patch, the deletion of old GTID rows happens asynchroneously and
slightly non-deterministic. Thus the number of old rows in
mysql.gtid_slave_pos can temporarily exceed @@gtid_cleanup_batch_size. But
all old rows will be deleted eventually after sufficiently many new GTIDs
have been replicated.

only --datadir option is tested in this test.
Other options (notably --password and --service) would need another,
more comprehensive test.

merge_role_db_privileges() was remembering pointers into Dynamic_array
acl_dbs, and later was using them, while pushing more elements into the
array. But pushing can cause realloc, and it can invalidate all pointers.

Fix: remember and use indexes of elements, not pointers.