wined3d: universal surface convertor function for unsigned integer color formats(5th attempt)

[Stefan Dosinger]

> I've changed things a bit and resubmitted patch. Now there will be less
> ifdefs.
> I'm not sure which "data types" are you talking about, since I'll need
> per-byte surface access in any case, and It doesn't look like it can be
> wrapped into endianness-independant datatype.
Maybe you could use bitmasks to access the single bytes