gdi32/tests: Use virtual screen size instead of primary monitor screen size.

[Peter Urbanec]

On 08/02/11 16:02, Marvin wrote:
> Full results can be found at
> http://testbot.winehq.org/JobDetails.pl?Key=9028
>
> Your paranoid android.
>
>
> === WNT4WSSP6 (32 bit clipping) ===
> clipping.c:438: Test failed: expected 0,0-0,0, got 0,0-800,600

It seems that GetSystemMetrics(SM_CXVIRTUALSCREEN) is supported on Win2k 
and later, but not on NT4. Presumably, on an NT4 system, the test could 
use GetSystemMetrics(SM_CXSCREEN) and it would work as long as there is 
only one monitor.

What's the proper incantation I need to use to detect NT4 and execute 
platform specific test code?