comctl32/tests: Add two casts to avoid comparisons of different int types.

[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
http://testbot.winehq.org/JobDetails.pl?Key=9229

Your paranoid android.


=== W7PROX64 (64 bit tab) ===
tab.c:1330: Test failed: got 69cc80, expected dededede