msvcrt: make WEOF returned from swscanf signed (try 2)

[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=16280

Your paranoid android.


=== WXPPROSP3 (32 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== W2K3R2SESP2 (32 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== WVISTAADM (32 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== W2K8SE (32 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== W7PRO (32 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== W7PROX64 (32 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== TEST64_W7SP1 (32 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== W7PROX64 (64 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff

=== TEST64_W7SP1 (64 bit msvcr90) ===
msvcr90.c:1149: Test failed: swscanf returns 0 instead of ffff