Cycles / OSL:
* Rename fresnel_dielectric() to fresnel_dielectric_cos() to match SVM, easier when searching code. 
* Also remove an old code comment in bsdf_reflection.h from Cycles branch days. 

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57035 954f8c5b-7b00-dc11-b283-0030488c597c