[2/2] gdi32/tests: fix MSVC build in bitmap.c

[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=14695

Your paranoid android.


=== WNT4WSSP6 (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 00416287

=== W2KPROSP4 (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 00416287

=== WXPPROSP3 (32 bit bitmap) ===
bitmap: unhandled exception 80000003 at 7C90120E

=== W2K3R2SESP2 (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 7C83F11C

=== WVISTAADM (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 7749653F

=== W2K8SE (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 00000000

=== W7PRO (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 772D5A15

=== W7PROX64 (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 00000000

=== TEST64_W7SP1 (32 bit bitmap) ===
bitmap: unhandled exception c0000005 at 77593CDB

=== W7PROX64 (64 bit bitmap) ===
Timeout

=== TEST64_W7SP1 (64 bit bitmap) ===
Timeout