Code cleanup: remove some unused cycles SSS code.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60693 954f8c5b-7b00-dc11-b283-0030488c597c
Fix crash running Blender in background mode, caused by revision 60633.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60694 954f8c5b-7b00-dc11-b283-0030488c597c
Fix dual quaternion armature deform giving erratic results in some cases. Bug
was encountered in a Kiribati rig file.

The problem was actually in the matrix to quaternion conversion function. One
problem is that it was using the wrong matrix indices in case of an ill defined
matrix trace. Besides that FLT_EPSILON was too small to detect cases where
float precision becomes a problem.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60695 954f8c5b-7b00-dc11-b283-0030488c597c