MacOS does not support OpenGL compatibility profile, so the following
changes had to be made:
- Replaced deprecated texture2D() with texture() in shaders
- Renamed `texture` uniform variable to `tex`, to avoid name conflict
- Use VAO, which is mandatory in OpenGL 3 core profile
- Create separate directories for source and header files.
- Build code shared between xsystem4 and aindump as a static library.
- Create header dirs gfx/ system4/ and vm/
- Make CG.c/h usable without a running VM
kichikuou