EMI: Big endian fixes

This makes the backgrounds draw properly for Big Endian machines. Outstanding issues are:
1. Actors are all black
2. The movies have incorrect colors

I'm not really sure if this should be merged as the TGA fix is probably wrong for the general case. I suspect that the swap should actually occur in the OpenGL driver, but I haven't figured out where/how to do that yet.

This shouldn't effect Grim, but it should be noted that on my Powerbook (in Linux) it looks like there's Z buffer issues which only render his top half.