ddraw/tests: Skip some tests when switching the display mode is not supported.

[Francois Gouget]

On Mon, 17 Feb 2014, Marvin wrote:
[...]
> ddraw4.c:5804: Test failed: Failed to set display mode, hr 0x80004001.

This failure is taken care of by the other SetDisplayMode() patch. All 
the other failures are unrelated to SetDisplayMode().


-- 
Francois Gouget <fgouget at codeweavers.com>