and so the engine calls current_thd to derive transaction information;
instead we now pass THD to those functions, it looks more logical
(it makes the implicit current_thd parameter more visible).
Approved by Brian and Monty.
Bugs fixed:
- Bug #20877: InnoDB data dictionary memory footprint is too big
- Bug #13544: Second delete of same row in transaction illustrates non-optimal locking
- Bug #20791: valgrind errors in InnoDB