ddraw/tests: Skip cubemap tests when cubemap isn't supported.

[Alexander Dorofeyev]

Stefan Dösinger wrote:
>> skip("No cubemap support\n");
> if you return right after that you wouldn't have to change the indention on all the rest of the code

There are some tests after that block not related to cubemap which I don't want 
to skip. Other options are moving cubemap block of code to the end (so that I 
can return then) or skipping the block by goto, but none of this are really 
better IMO.

> Also I think in the case of the surface test, there should be an easier way to tell if cubemaps are supported, without starting a d3d device. In the worst case just abort on a CreateSurface error

I spent some time looking for a better working option a while ago, but couldn't 
find anything working on Wine, Win98 (qemu) and XP. Will just check 
CreateSurface if that's ok.