ddraw/tests: Probe the supported display modes and skip tests based on the result.

[Henri Verbeet]

On 27 February 2014 02:24, Francois Gouget <fgouget at codeweavers.com> wrote:
>  * QEmu can emulate an old Cirrus 5446 graphics card that tops out at
>    24bpp and thus does not support the 32bpp modes we want. For Windows
>    2000 that's all that works.
>
For most of these tests, perhaps all of them, we don't care about the
difference between 24 and 32 bpp modes. I'm going to look into writing
a small set_display_mode() helper that just tries both, which would
allow these tests to be run on the Windows 2000 testbot as well. That
doesn't help for 8 bpp modes, but there are only a few tests that need
those, and I think the way we handle those currently is fine.