Simplifying fragment shader code to match what can compile and run on mac Core profile.  Removing enable/disable calls not supported by mac core profile.  Adding lots of gl error checks.  Clearing spurious gl error failure after glew init.
Simplifying fragment shader code to match what can compile and run on mac Core profile.  Removing enable/disable calls not supported by mac core profile.  Adding lots of gl error checks.  Clearing spurious gl error failure after glew init.

sensics/OSVR-RenderManager,sensics/OSVR-RenderManager,sensics/OSVR-RenderManager