A number of games make an EFB copy in I4/I8 format, then use it as a
texture in C4/C8 format. Detect when this happens, and decode the copy on
the GPU using the specified palette.
This has a few advantages: it allows using EFB2Tex for a few more games,
it, it preserves the resolution of scaled EFB copies, and it's probably a
bit faster.
D3D only at the moment, but porting to OpenGL should be straightforward..
