Merge from Percona Server enforced use of a specific storage engine
authored by Stewart Smith.

Modified to be session variable and modifiable only by SUPER. Use
similar implementation as default_storage_engine.

- Renaming Item::is_bool_func() to is_bool_type(), to avoid assumption
  that the item is an Item_func derivant.
- Deriving Item_func_spatial_rel from Item_bool_func rather than Item_int_func

fixed embedded server tests
MDEV-7009: SET STATEMENT min_examined_row_limit has no effect
MDEV-6948:SET STATEMENT gtid_domain_id = ... FOR has no effect (same for gtid_seq_no and server_id)

old values of SET STATENENT variables now saved in its own Query_arena and restored later

the problem was in assigning default value during parsing.

(changes of backported patch are very small: strlen removed, error processing fixed, view open statistics added)

Double error reporting removed.

* watch for "redefined macro" warning
* don't enable -D_FORTIFY_SOURCE=2 in debug builds (it requires -O)

common parent class for Item_func_isnull and Item_func_isnotnull

Add holder thread_id, file_name and line to output.

MDEV-7025 ANALYZE SELECT/INSERT/UPDATE/DELETE from a view does not check access permissions on the view

Added access checking for the ANALYZE statement command.

Fix Item_ident::print() to work when there is no current database

Change r_rows to be double

add forgotten initialization of the mutex name

disable a broken test, pending a proper fix

otherwise innodb plugin might invoke xtradb function with the same name,
and that might crash (./mtr --emb innodb.strict_mode)

update test results after the fix

safe_process puts its children (mysqld, in this case) into a separate
process group, to be able to kill it all at once.

buildslave kills mtr's process group when it loses connection to
the master.

result? buildslave kills mtr and safe_process, but leaves stale
mysqld processes in their own process groups.

fix: put safe_process itself into a separate process group, then
buildslave won't kill it and safe_process will kill mysqld'd
and itself when it will notice that the parent mtr no longer exists.

Analysis: after a red-black-tree lookup we use node withouth
checking did lookup succeed or not. This lead to situation
where NULL-pointer was used.

Fix: Add additional check that found node from red-back-tree
is valid.

Re-applied lost in the merge revision:
commit ed313e8a
Author: Sergey Vojtovich <svoj@mariadb.org>
Date:   Mon Dec 1 14:58:29 2014 +0400

    MDEV-7148 - Recurring: InnoDB: Failing assertion: !lock->recursive

    On PPC64 high-loaded server may crash due to assertion failure in InnoDB
    rwlocks code.

    This happened because load order between "recursive" and "writer_thread"
    wasn't properly enforced.

Analysis: On master when executing (single/multi) row INSERTs/REPLACEs
InnoDB fallback to old style autoinc locks (table locks)
only if another transaction has already acquired the AUTOINC lock.
Instead on slave as we are executing log_events and sql_command
is not correctly set, InnoDB does not use new style autoinc
locks when it could.

Fix: Use new style autoinc locks also when
thd_sql_command(user_thd) == SQLCOM_END i.e. this is RBR event.

Merged https://github.com/facebook/mysql-5.6/commit/615dd07d900ce08948340b6c11e37fd1d2a91065 from https://github.com/facebook/mysql-5.6/
authored by rongrong. Removed C++11 requirement by using
std::map instead of std::unordered_set.

Add analysis to leaf pages to estimate how fragmented an index is
and how much benefit we can get out of defragmentation.

Conflicts:
	sql/log.cc
	sql/rpl_rli.cc
	sql/sql_repl.cc

MDEV-6403: Temporary tables lost at STOP SLAVE in GTID mode if master has not rotated binlog since restart

The binlog contains specially marked format description events to mark
when a master restart happened (which could have caused temporary
tables to be silently dropped). Such events also cause slave to close
temporary tables.

However, there was a bug that if after this, slave re-connects to the
master in GTID mode, the master can send an old format description
event again. If temporary tables are closed when such event is seen
for the second time, it might drop temporary tables created after that
event, and cause replication failure.

With this patch, the restart flag of the format description event is
cleared by the master when it is sent to the slave in a subsequent
connection, to avoid the errorneous temp table close.

MDEV-6589: Incorrect relay log start position when restarting SQL thread after error in parallel replication

The problem occurs in parallel replication in GTID mode, when we are using
multiple replication domains. In this case, if the SQL thread stops, the
slave GTID position may refer to a different point in the relay log for each
domain.

The bug was that when the SQL thread was stopped and restarted (but the IO
thread was kept running), the SQL thread would resume applying the relay log
from the point of the most advanced replication domain, silently skipping all
earlier events within other domains. This caused replication corruption.

This patch solves the problem by storing, when the SQL thread stops with
multiple parallel replication domains active, the current GTID
position. Additionally, the current position in the relay logs is moved back
to a point known to be earlier than the current position of any replication
domain. Then when the SQL thread restarts from the earlier position, GTIDs
encountered are compared against the stored GTID position. Any GTID that was
already applied before the stop is skipped to avoid duplicate apply.

This patch should have no effect if multi-domain GTID parallel replication is
not used. Similarly, if both SQL and IO thread are stopped and restarted, the
patch has no effect, as in this case the existing relay logs are removed and
re-fetched from the master at the current global @@gtid_slave_pos.