WIP: Compiling again after changes for GLES2.0 support. More work needed to actually support GLES2.0
WIP: HelloPangolin example now working as-is with GLES2
WIP: Implement more backward compatibility methods for GLES2.
WIP: Implement matrix stacks.
WIP: Backward compatible GLES2.0 support for texturing.
WIP: Fix GLES2.0 text rendering.
WIP: Small fixes.