New Feature:
========
This feature adds a safe replacement to the
MASTER_USE_GTID=Current_Pos option for CHANGE MASTER TO as
MASTER_DEMOTE_TO_SLAVE=<bool>. The use case of Current_Pos is to
transition a master to become a slave; however, can break
replication state if the slave executes local transactions due to
actively updating gtid_current_pos with gtid_binlog_pos and
gtid_slave_pos.
MASTER_DEMOTE_TO_SLAVE changes this use case by forcing users to set
Using_Gtid=Slave_Pos and merging gtid_binlog_pos into gtid_slave_pos
once at CHANGE MASTER TO time. Note that if gtid_slave_pos is more
recent than gtid_binlog_pos (as in the case of chain replication),
the replication state should be preserved.
Additionally, deprecate the `Current_Pos` option of MASTER_USE_GTID
to suggest the safe alternative option MASTER_DEMOTE_TO_SLAVE=TRUE.
Reviewed By:
============
Andrei Elkin <andrei.elkin@mariadb.com>
- created binlog_encryption test suite and added it to the default list
- moved some tests from rpl, binlog and multisource suites to extra
so that they could be re-used in different suites
- made minor changes in include files
