Use GL_BGRA for 32 bit textures on Windows

25% improvement in Popolocrois, probably decent gains in other games using 32-bit textures often.  FF2 for example doesn't, and most games of course aren't constantly reuploading textures.

I'm not sure if this will be better on ATI/Intel, but many people online suggest that it's "better on Windows."  I'm guessing this applies to all desktops, but for now just enabled on Windows.

On my Android, I tried GL_EXT_texture_format_BGRA8888 (which requires the internal format be set also), but it did not improve performance at all, and maybe hurt it.  At least on Adreno.

-[Unknown]