[COMCTL32] Workaround v6 button redraw regressions CORE-13278 & CORE-16093

[COMCTL32] Workaround v6 button redraw regressions CORE-13278 & CORE-16093

Most likely not correct, as it breaks comctl32:buttonv6 tests
https://reactos.org/testman/compare.php?ids=68146,68147

But greatly eliminates perceived flickering when hovering
with the mouse about buttons in unthemed mode.
We suffered from these regressions for years and nobody did
find a proper solution, therefore it's time to at least workaround them.
The patch did not expose any new real-world-issues after I retested
the whole rapps suite against it in 0.4.12RCs.

I committed the same workaround already into 0.4.12-RC-30-g
9513c9bf12926e82c6956910366e661539789933

CORE-13278 was once introduced/unhidden by SVN 73806 ==
c607de714cefce7ce0acc2cdf15837f3bcf3d6dd

CORE-16093 was once introduced/unhidden by SVN 74149 ==
301c47607451bbf47331983f842cb9470bfe53e5