Cycles / SunSky:
* Use already calculated theta^2 for theta^3 calculation. 

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55634 954f8c5b-7b00-dc11-b283-0030488c597c
Merge branch 'trunk' of https://github.com/nicholasbishop/blender into trunk