Recommit with an Windows build fix:

Recommit with an Windows build fix:
Fix inconsistencies
- memory allocated with spprintf, or likes, outside of mysqlnd's
allocator functions should not be freed by the mysqlnd's allocator
(a wrapper around emalloc/malloc).
- memory allocated by the mysqlnd's allocator should only be freed
  by it.
- add a mode to track memory usage (malloc/free)