Added 'final' to some classes to improve generated code

Final added to:
- All reasonable classes inhereted from Field
- All classes inhereted from Protocol
- Almost all Handler classes
- Some important Item classes

The stripped size of mariadbd is just 4K smaller, but several object files
showed notable improvements in common execution paths.
- Checked field.o and item_sum.o

Other things:
- Added 'override' to a few class functions touched by this patch.
- Removed 'virtual' from a new class functions that had/got 'override'
- Changed Protocol_discard to inherit from Protocol instad of Protocol_text

1 files changed, 1 insertions, 1 deletions

diff --git a/storage/blackhole/ha_blackhole.h b/storage/blackhole/ha_blackhole.h
index 646fba6da9f..c2a36a68f45 100644
--- a/storage/blackhole/ha_blackhole.h
+++ b/storage/blackhole/ha_blackhole.h
@@ -36,7 +36,7 @@ struct st_blackhole_share {
   Class definition for the blackhole storage engine
   "Dumbest named feature ever"
 */
-class ha_blackhole: public handler
+class ha_blackhole final : public handler
 {
   THR_LOCK_DATA lock;      /* MySQL lock */
   st_blackhole_share *share;