sql/event.cc:
  -my_error() as close as possible to the place where the error
   occurs.
  -a thought how to replicate events
  -use close_thread_tables() in some cases and for others rely on
   this call being done in sql_parse.cc::do_command()
sql/event.h:
  remove redundant defines
sql/event_executor.cc:
  - reenable the compilation again
  - don't backup the open_tables_state, it's not needed
sql/event_timed.cc:
  - inline a bit
  - comment added
sql/mysqld.cc:
  - start mysqld with --event-scheduler=0 by default
sql/share/errmsg.txt:
  3 new messages
sql/sql_parse.cc:
  remove now obsolete error checking - the errors are reported
  as closer as possible to the place where they are detected
sql/sql_yacc.yy:
  add WARNING message. fix a bug that was corrupting 
  thd->client_capabilites ->
  select count(*) from mysql.event
  was reporting : "Unknown table test.event"!!!
  Using temporal variable is nice but IMO quite error-prone.