Probe the GL_RENDERER string on Nvidia to grab the driver version.
Fix for previous commit. I was supposed to use GL_VERSION, not GL_RENDERER.
Slight optimization in the pixel shader. We are using pow(2.0, X) in place of exp2(X). This can be faster in places that don't optimize a pow to a exp2 in this case.
Notice this from here: http://cgit.freedesktop.org/mesa/mesa/commit/?id=847bc36a38d42967ad6bf0492fe90a4892d9d799
Intel Haswell GPU is 24 cycles for POW and 14 cycles for EXP2.
Maybe other GPUs don't optimize this either. Just be safe.