Defer binding to the dax opengl interop call
Verify that we have openGL 2.1 which is what we need, not 3.2
If opengl interop fails these should be execution errors not bad values.
Move the VerifyThresholdTopology to a separate header to make cuda 5.5 happy.

CUDA 5.5 using the new clang support was failing to find the worklet
when it existed in the same file as the calling code. Moving the worklet
to a separate header fixed the problem.
Throw errors if opengl/cuda interop fails, or setting a specific cuda device
Make sure we don't transfer anything to the cuda before we establish interop.
Merge branch 'improve-mandlebulb-lighting'
Merge branch 'cuda5_5_and_xcode_5'
Merge branch 'better_opengl_error_messages'
Remove error checking from transfer to gl.
Try to improve performance by releasing execution memory when possible.

This execution memory is going to be recomputed so no need to keep it on
the device.
Merge branch 'improve_interop_perf'