Fix: view plane for sculpting did not work correctly for rotated
objects. Reuse the object space view vector. Also, minor cleanup, reused
cache values instead of requering.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56135 954f8c5b-7b00-dc11-b283-0030488c597c