- split into several files
- forbid parallel execution (before analyse is done how to make it possible)
  because the same sp_head instance cannot be executed in parallel
- added GPL headers
- changed EVENT_ACL to be per DB variable
- fixed minor problems


mysql-test/lib/init_db.sql:
  WL#1034 updated
  - add Event_priv to mysql.user (update test)
  - add updated mysql.event table struct
scripts/mysql_fix_privilege_tables.sql:
  WL#1034 updated
  add updated mysql.event structure
sql/Makefile.am:
  split event.cc into
  - event.cc (create/alter/drop)
  - event_executor.cc (main and worker threads)
  - event_timed.cc (class event_timed)
  - event_priv.h (some definitions used internally by the module)
sql/event.cc:
  - added GPL header
  - split into few files
  - fixed some issues after code review
  - now using SP routines for opening/traversing/closing tables
    (will be reverted)
sql/event.h:
  - add GPL header
  - remove two methods - inline them in sql_yacc.yy 
  - don't use absolute values for EVEX_ defines but the SP_ equivalents (have to move 100% to SP_
    defines and as later step to not transfer messages upwards in the stack but
    report them at the place they occur)
  - updated reference table definition
  - move default mem_root param from event.cc to the header
sql/mysqld.cc:
  WL#1034
  rename --event-executor to --event-scheduler
  executor sounds a bit scary :)
sql/set_var.cc:
  rename internal variable name from event_executor to event_scheduler
  (ppl won't be scarried anymore :)
sql/share/errmsg.txt:
  omit one %s - not needed
sql/sp_head.cc:
  disable this DBUG_PRINT for a bit. m_next_cached_sp is 0x0 and I get crash here...
sql/sp_head.h:
  remove m_old_cmq, a temporal variable is used in sql_yacc.yy (Serg's idea)
  to keep the previous state.
  $<ulong_val>$ =  ....
  
  YYTHD->client_capabilites != $<ulong_val>4;
  
  (the same is done also for class event_timed)
sql/sql_acl.cc:
  handle pre-5.1.4 table and give the user EVENT_ACL if he had CREATE_ACL
sql/sql_acl.h:
  fix the bitmask
sql/sql_parse.cc:
  - move from EVENT_ACL being global to EVENT_ACL being per DB like
    CREATE_PROC_ACL
  - lex->m_qname dropped, because not needed, fix code therefore
  - add comment that SHOW CREATE EVENT has to be implemented
sql/sql_yacc.yy:
  - use temporal variable of Bison to store a short lived value
  - fix indentation
  - inline 2 class event_timed methods in the parser
sql/tztime.h:
  be more expressive - it's already extern