Blender Git Loki

Fix T70476: Sculpting with Subsurf on top produces artifacts

The issue was caused by crazy space distortion orientation happening
for subsurf modifier.

Solved by making it so subsurf only deforms the surface but keeps
matrices as-is. This is not fully mathematically correct, but is better
that the fall-back solution which was doing wrong matrices anyway.
Also, this is closer to have subsurf was handled prior to the
related changes.

Reviewed By: brecht, pablodp606

Differential Revision: https://developer.blender.org/D5991