CORE-11569, CORE-19684
Addendum to commit 71bed0f5f8 (PR #7123).
The problem in uxtheme was introduced in commit 685084b63c (as part
of a fix for CORE-17203), because it was a copy-paste and adaptation
of the corresponding code in `ntuser/nonclient.c!NC_DoButton()`.
The bugs in `win32ss/user/ntuser/defwnd.c` (and `nonclient.c` as fixed by
the previous commit) were in turn introduced from the migration of menu
and related code from user32 to win32k, see commit 6dfa71c487 (r68904).
c02289a08a