WineD3D: Make CreateCubeTexture fail when not supported

[Felix Nawothnig]

Luke Bratch wrote:
> Somewhere I have an ancient Matrix MGA G200 AGP
> card...  If this would be of any use, I'll dig it out
> and run any tests in Wine/Windows that you'd like?

Sure, if you're willing to do that just because I'm lazy. :-) I was just 
hoping someone might be running a box with an MGA and Windows installed 
as I'd have to reconnect my CDROM drive, steal a HDD from my brother and 
install Windows first.

Felix