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/sql_window.cc

@@ -2799,7 +2799,7 @@ bool compute_window_func(THD *thd,
 
       /* Check if we found any error in the window function while adding values
          through cursors. */
-      if (thd->is_error() || thd->is_killed())
+      if (unlikely(thd->is_error() || thd->is_killed()))
         break;