Now whenever we reach the GTID point requested from the slave (when using GTID
position to connect), we send a fake Gtid_list event. This event is used by
the slave to know the current old-style position for MASTER_POS_WAIT(), and
later the similar binlog position for MASTER_GTID_WAIT().

Without this fake event, if the slave is already fully up-to-date with the
master, there may be no events sent at the given position for an indeterminate
time.