glsl: Convert tuple into a class
glsl: Convert tuple into a class

This makes things a little more clear now, and it will make future
changes... possible.

Signed-off-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>
Acked-by: Dylan Baker <dd378c4ca75f71f527acddef5b43fc35b68d5b7a@pnwbakers.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler