Fix windows build

Sync .cpp files with recent changes
Push everything under the 'OpenApoc' namespace

I was having issues with symbol collisions with the X headers (required
for opengl on linux), so hopefully this should help with that
Force OpenGL use

I intend to directly use opengl to render some stuff that doesn't seem
to map well to allegro's bitmap drawing routines (palette blending etc.)
Merge branch 'master' into WIP/win-deps