sql/event_timed.cc:
  After merge fixes: dbname can never be NULL.
sql/events.cc:
  After merge fixes: use a new signature of sp_use_new_db
sql/sp_head.cc:
  After merge fixes: replace assert with an if for events code to work.
sql/sql_parse.cc:
  After merge fixes: put back free_items, it's used in partitioning.
  Whether it is not a bug is to be investigated.
  Remove check_db_used, as planned.