wined3d: Add support for updating part of a compressed surface.

[Henri Verbeet]

2008/9/6 Christof Sigel <christof.sigel at intenode.on.net>:
> Thanks for the input, I really should have realised my approach was
> incorrect as soon as I saw that DXT textures are in blocks.
> I'm not quite sure how to go about writing a test case, would I just
> have to create and update surface(s) and check that the resulting
> surface(s) have been updated correctly?
>
Pretty much.