sql/event.cc:
  - fix TODO (remove things already done)
  - check the length of the event's name and body during creation
    and report an error if longer than what can be fit into 
    mysql.event (nothing like non-strict mode here)
  - report to sql_parse.cc and error when open table failed, otherwise send_ok()
    was being called and the error have become an warning.
  - update function documentation a bit
  - evex_db_find_routine_aux returns 0 and not EVEX_OK
sql/event_executor.cc:
  - CS changes to definitions of the main and worker thread routines
  - reorder code a bit to prevent crashes because of reading of
    already freed data -> first wait all events to finish their work,
    namely all worker threads to finish, and then destroy in-memory
    structures
  - more error checking and error reporting at the place of failure.
sql/event_priv.h:
  code simplifying macro
sql/event_timed.cc:
  CS cosmetics