Add likely/unlikely to speed up execution

Added to:
- if (error)
- Lex
- sql_yacc.yy and sql_yacc_ora.yy
- In header files to alloc() calls
- Added thd argument to thd_net_is_killed()

sql/event_data_objects.cc

@@ -1444,7 +1444,7 @@ Event_job_data::execute(THD *thd, bool drop)
   }
 
 end:
-  if (drop && !thd->is_fatal_error)
+  if (drop && likely(!thd->is_fatal_error))
   {
     /*
       We must do it here since here we're under the right authentication