Fix: texture scaling for sculpting is different between overlay and
stroke. The reason is that we use a different sampling function.
Reported by Michalis Zissiou, thanks!

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56097 954f8c5b-7b00-dc11-b283-0030488c597c