ddraw/tests: Use wine_dbgstr_rect() in the ddraw4 tests.

[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=23461

Your paranoid android.


=== w864 (32 bit ddraw4) ===
ddraw4.c:7999: Test failed: Got unexpected P8 color key blit result.

=== w1064 (32 bit ddraw4) ===
ddraw4.c:2540: Test failed: Expected (0,0)-(512,384), got (0,0)-(1024,768).
ddraw4.c:7999: Test failed: Got unexpected P8 color key blit result.

=== w1064 (64 bit ddraw4) ===
ddraw4.c:2540: Test failed: Expected (0,0)-(512,384), got (0,0)-(1024,768).
ddraw4.c:7999: Test failed: Got unexpected P8 color key blit result.