Recompiling the entire program whenever a shader changes is slow, and it
can interrupt flow. Shader reloads are essentially instantaneous now. If
the new shader fails to compile, no state is changed; the previous
program continues to be used.
Uses the GL_ARB_blend_func_extended to get single-pass, per-channel
alpha blending. gl_generator is now used instead of gl to enable the
extension.
The background color is removed since that presumably needs to run in a
separate pass.
This function isn't exactly useful, but it's working ffi with the
fontconfig library. Woo! Next step will be returning some objects with
more information (like font path so we can start rendering glyphs!).
