remove assert

sql/event_data_objects.cc:
  add a comments that using gmt_sec_to_TIME() won't
  be safe after 2038. per andrey's request
sql/event_queue.cc:
  remove assert, which aborts server in the case when it shouldn't

sql/event_queue.cc

@@ -160,7 +160,6 @@ Event_queue::init_queue(THD *thd, Event_db_repository *db_repo)
   {
     sql_print_error("SCHEDULER: sizeof(my_time_t) != sizeof(time_t) ."
                     "The scheduler may not work correctly. Stopping");
-    DBUG_ASSERT(0);
     goto err;
   }