This untangles some of the gigantic kitchen sink headers
in an attempt to split things into smaller files.
Also don't include gl.h, glext.h, windows.h,
and other such nonsense *everywhere*.
Lots of cleanups on the way too. More dead/unused code removal.
Remove incrFlag(), decrFlag() Lua functions.
This allows attaching multiple shader programs, processing the entire
screen as texture. Chaining shaders works, each shader will use
the output of the previous shader as input.
