Minor "to do" items are identified in the source code with "TODO..." comments.

Major items to do:

* Use the new versioning infrastructure to identify all errors specific to
  - profile
  - extension
  - version
  - stage
  
* Add semantics and productions for all new grammar (1.2 through 4.3)
	1.2
	 - uniform initializers
	 - non-square matrices
	 - centroids/multisample
	 - gl_PointCoord

	1.3
	 - integer ops
	 - integer built-in functions
	 - switch
	 - bunch of new built-ins
	 - noperspective

	1.4
	 - uniform blocks
	 - layout qualifiers
	 - texture buffers

	1.5
	 - geometry shaders

	3.3
	 - ...

* Replace the preprocessor with a better one.

* Verify/fix thread safety of the parse context.