Merge master, Kuwahara optimizations

Optimized Kuwahara filter a bit
Added Kuwahara radius 3 filter which is heavily optimized and can
process 4 megapixel images without issue
Revert "Merge master, Kuwahara optimizations"

This reverts commit 9655f16e89caf35878ac7d2f3e2646568a5a670a.
Merge branch 'master' of git://github.com/BradLarson/GPUImage
Kuwahara filter optimizations
Merge pull request #797 from jjxtra/master

Kuwahara filter optimizations