JSON file of symbols to restrict symbol generation

[slimsag]

One of my lasting concerns is the side of the wrappers generated by Glow. For instance Azul3D has an OpenGL 2 renderer (http://github.com/azul3d/gfx-gl2) that uses a somewhat small subset of the OpenGL 2.0 API.

Since most of the symbols (enums and functions) generated by Glow are not actually used by us -- it seems silly to compile them at all. I'd like to be able to specify a JSON input file to Glow that would specify the symbols that we actually want, for example:

{
    "Enums": [
        "GL_CCW",
        "GL_COLOR_ATTACHMENT0",
        "GL_COMPRESSED_RGB"
    ],
    "Functions": [
        "glBindTextures",
        "glBindVertexArray"
    ]
}

And Glow could generate just those symbols, greatly reducing the compilation time. Although I think it's not strictly the same tactic -- this could also help others trying to deal with issue #23