Make the binlog handlerton participate in START TRANSACTION WITH CONSISTENT
SNAPSHOT, recording the binlog position corresponding to the snapshot taken
in other MVCC storage engines.

Expose this consistent binlog position as the new status variables
binlog_trx_file and binlog_trx_position. This enables to get a fully
non-locking snapshot of the database (including binlog position for
slave provisioning), avoiding the need for FLUSH TABLES WITH READ LOCK.

Modify mysqldump to detect if the server supports this new feature, and
if so, avoid FLUSH TABLES WITH READ LOCK for --single-transaction
--master-data snapshot backups.