d3d: Avoid rewriting textures, just swizzle.

Luckily A is in the same place and the same width, so we can do this for
all but framebuffers easily.

Technically we could do it in OpenGL as well.

Small (1-2%) performance improvement in FF2.
d3d: Correctly disable stencil testing.
Merge pull request #6801 from unknownbrackets/d3d

d3d: Avoid rewriting textures to BGRA from RGBA, just swizzle