The Modular Shader Language (MSL) is a pre-compiled shader language
with multiple targets. It is effectively a wrapper around GLSL and
relies on external tools to handle the main work of the compilation.

The primary goals are:
* Provide an environment more similar to other compiled languages,
  such as access to a preprocessor and compile-time errors that point
  to the file.
* Allow targeting multiple platforms with different capabilities with
  the same source.
* Relies on official and external tools as much as possible. This
  makes the language easier to extend and maintain and allows other
  third party tools, such as optimizers, to be used.
* Allows all stages of the pipeline to be specified in the same
  source. This gives more flexibility in how you organize your source.
* Allows for render states and sampler states to be declared in the
  shader. This gives more flexibility in client applications by
  allowing these to be set in the shader without hard-coding them in
  the application.
* Pipeline is linked when compiling the shader modules, allowing for
  earlier checks and easier loading of shaders in the final
  application.