Extend existing plugins to support
* SHOW QUERY_RESPONSE_TIME
* FLUSH QUERY_RESPONSE_TIME
* SHOW LOCALE
move userstat tables to use the new API instead of
hand-coded syntax
sql/sp_head.cc:
Trigger MYSQL_AUDIT_GENERAL_STATUS event for each statement in stored
procedures. Not strictly needed for query_response_time plugin, but
makes it behave more like Percona patch.