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/heap/ha_heap.h b/storage/heap/ha_heap.h
index 50d3c0afb6c..3a41028c719 100644
--- a/storage/heap/ha_heap.h
+++ b/storage/heap/ha_heap.h
@@ -25,7 +25,7 @@
 #include <heap.h>
 #include "sql_class.h"                          /* THD */
 
-class ha_heap: public handler
+class ha_heap final : public handler
 {
   HP_INFO *file;
   HP_SHARE *internal_share;