First part of fix for BUG#7998 "Replication should be more clever about when to replicate RELEASE_LOCK()"
(next part is updating test results)


sql/item_func.cc:
  no need for binlogging DO RELEASE_LOCK() anymore. Make GET_LOCK() do nothing in slave thread.
sql/log_event.cc:
  comment fixes
sql/mysqld.cc:
  warning removed
sql/slave.cc:
  fix after merge