new features:
set event_scheduler=ON|OFF will now try to init event scheduler
if it's not enabled
set event_scheduler=default will try to enable it based on
the value of the event_scheduler when mysqld was started

reload grant tables.

cherry-picked 7454f1c5 from 10.1

Check allows zero lengts int/uint now.

When CHANGE MASTER was executed as a PS, its attributes were wrongly
getting reset toward the end of PREPARE. As a result, the subsequent
executions had no effect. Fixed by making sure that the CHANGE MASTER
attributes are preserved during the lifetime of the PS.

When CHANGE MASTER was executed as a PS, its attributes were wrongly
getting reset toward the end of PREPARE. As a result, the subsequent
executions had no effect. Fixed by making sure that the CHANGE MASTER
attributes are preserved during the lifetime of the PS.

* update *.result files
* fix XtraDB for Windows (again)

* OSX (mysqlimport freeing unallocated memory)
* Windows (didn't compile MSI)
* fulltest2 (innodb crashes in --embedded --big)

Just "Master" could be understood as the master IP or hostname and thus can
cause confusion to db admins. "Master connection name" clearly states that
the log line contains connection name in the (possibly) multi-master setup.

it was never doing anything anyway

make_cond_for_info_schema() does preserve outer fields

MDEV-8685 MariaDB fails to decode Anonymous_GTID entries
MDEV-5705 Replication testing: 5.6->10.0

- Ignoring GTID events from MySQL 5.6+ (Allows replication from MySQL 5.6+ with GTID enabled)
- Added ignorable events from MySQL 5.6
- mysqlbinlog now writes information about GTID and ignorable events.
- Added more information in error message when replication stops because of wrong information in binary log.
- Fixed wrong test when write_on_release() should flush cache.

(even when configured with --binlog-format=statement).
Before we got an error on the slave and the slave stopped if the master
was configured with --binlog-format=mixed or --binlog-format=row.

When we calculate max_key_len for RANGE_OPT_PARAM::min_key/max_key, take
into account that QUICK_RANGE::QUICK_RANGE for some reason assumes
that there is one more byte there:

      max_key((uchar*) sql_memdup(max_key_arg,max_length_arg+1)),

EXPLAIN INSERT ... SELECT tried to use SELECT's execution path. This
caused a collection of problems:
- SELECT_DESCRIBE flag was not put into select_lex->options, which
  means it was not in JOIN::select_options either (except for the first
  member of the UNION).
- This caused UNION members to be executed. They would attempt to write
  join output rows to the output.
- (Actual cause of the crash) second join sibling would call
  result->send_eof() when finished execution. Then,
  Explain_query::print_explain would attempt to write to query output
  again, and cause an assertion due to non-empty query output.

Substitute into transformed subselects original left expression and than register its change in case it was substituted.

MDEV-7565: Server crash with Signal 6 (part 2)

followup test suite and its fix.

Problem was in rewriting left expression which had 2 references on it. Solved with making subselect reference main.

Item_in_optimized can have not Item_in_subselect reference in left part so type casting with no check is dangerous.

Item::cols() should be checked after Item::fix_fields().