Cycles OpenCL: make displacement and world importance sampling work.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57636 954f8c5b-7b00-dc11-b283-0030488c597c
Fix #35812: cycles image texture node not doing proper alpha handling of PNG
images with open shading language enabled.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57637 954f8c5b-7b00-dc11-b283-0030488c597c