WL#3337 (Event scheduler new architecture)

Third cut to simplify parsing phase. Now DROP EVENT works.

Overloaded few functions to be able to use either sp_name or pass two LEX_STRINGs
instead of a Event_timed pointer. This is transitional and eventually the old
functions will be removed. For now DROP EVENT also works, does not need anymore
a parsing object (Event_timed) and definer initialization because everyone who
has EVENT_ACL can drop events, and this is checked on execution time in sql_parse.cc
from the security context, as it should be.


sql/event_data_objects.cc:
  overload few functions
sql/event_scheduler.cc:
  Event_scheduler::drop_event() actually does not need Event_timed object
  but just an identifier, hence pass only sp_name.
  
  Overloaded Event_scheduler::find_event() to work with sp_name object. Eventually
  the old version will be removed. This is being done as transitional step to
  be able to test frequently code.
sql/event_scheduler.h:
  Event_scheduler::drop_event() actually does not need Event_timed object
  but just an identifier, hence pass only sp_name.
  
  Overloaded Event_scheduler::find_event() to work with sp_name object. Eventually
  the old version will be removed. This is being done as transitional step to
  be able to test frequently code.
sql/events.cc:
  Change db_drop_event() not to use Event_timed, either coming from parsing
  or from Event_timed::drop, but use LEX_STRINGs. sp_name is not convinient
  because in Event_timed::drop a temporary object has to be created. Hence, 
  dereference the sp_name in Events::drop_event() and pass the LEX_STRINGs.
sql/events.h:
  Change db_drop_event() not to use Event_timed, either coming from parsing
  or from Event_timed::drop, but use LEX_STRINGs. sp_name is not convinient
  because in Event_timed::drop a temporary object has to be created. Hence, 
  dereference the sp_name in Events::drop_event() and pass the LEX_STRINGs.
sql/events_priv.h:
  Change db_drop_event() not to use Event_timed, either coming from parsing
  or from Event_timed::drop, but use LEX_STRINGs. sp_name is not convinient
  because in Event_timed::drop a temporary object has to be created. Hence, 
  dereference the sp_name in Events::drop_event() and pass the LEX_STRINGs.
sql/sql_parse.cc:
  SQLCOM_DROP_EVENT does not need lex->event_parse_data object and 
  is more like SQLCOM_SHOW_CREATE_EVENT. Therefore, move it to the block that
  handles the latter.
sql/sql_yacc.yy:
  DROP EVENT does not need a parsing object, just a name.
  Store it as lex->spname. Pretty similar handling to the one of
  SHOW CREATE EVENT.

sql/event_data_objects.cc

@@ -1299,7 +1299,7 @@ Event_timed::drop(THD *thd)
   uint tmp= 0;
   DBUG_ENTER("Event_timed::drop");
 
-  DBUG_RETURN(db_drop_event(thd, this, false, &tmp));
+  DBUG_RETURN(db_drop_event(thd, dbname, name, false, &tmp));
 }
 
 
@@ -1903,8 +1903,62 @@ bool
 event_timed_identifier_equal(Event_timed *a, Event_timed *b)
 {
   return event_timed_name_equal(a, &b->name) &&
-         event_timed_db_equal(a, &b->dbname) &&
-         event_timed_definer_equal(a, &b->definer);
+         event_timed_db_equal(a, &b->dbname);
+}
+
+
+/*
+  Checks whether two events have the same name
+
+  SYNOPSIS
+    event_timed_name_equal()
+
+  RETURN VALUE
+    TRUE  names are equal
+    FALSE names are not equal
+*/
+
+bool
+event_timed_name_equal(sp_name *name, LEX_STRING *event_name)
+{
+  return !sortcmp_lex_string(name->m_name, *event_name, system_charset_info);
+}
+
+
+/*
+  Checks whether two events are in the same schema
+
+  SYNOPSIS
+    event_timed_db_equal()
+
+  RETURN VALUE
+    TRUE  schemas are equal
+    FALSE schemas are not equal
+*/
+
+bool
+event_timed_db_equal(sp_name *name, LEX_STRING *db)
+{
+  return !sortcmp_lex_string(name->m_db, *db, system_charset_info);
+}
+
+
+/*
+  Checks whether two events are equal by identifiers
+
+  SYNOPSIS
+    event_timed_identifier_equal()
+
+  RETURN VALUE
+    TRUE   equal
+    FALSE  not equal
+*/
+
+bool
+event_timed_identifier_equal(sp_name *a, Event_timed *b)
+{
+  return event_timed_name_equal(a, &b->name) &&
+         event_timed_db_equal(a, &b->dbname);
 }