[1/2] user32/tests: Add some tests to show that WS_CLIPCHILDREN doesn't exclude children from update region.

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=14817

Your paranoid android.


=== wvistau64 (64 bit msg) ===
msg.c:10561: Test failed: expected PeekMessage to return FALSE, got 1