Port over optimizations; texturing to browser path.
Remove an optimization attempt that has too little effect.
Minor optimization and rid of warning.

The shader program needs things to be set that ground plane rendering
doesn't set. So just move ground render after track to get rid of the
one warning (first frame only). It doesn't matter because ground
rendering is just for debugging and will go away.
Note extraction target location.
Get GL context from goglfw window (in a platform-independent way).