Blender Git Loki

Skip subsurf normal allocation/calculation when not needed.

CCGSubsurf has already a function to disable calculation of normals,
but seems it wasn't used. This patch changes subsurf UV and
subsurf_calculate_limit_positions() to not calculate normals, and also
not allocate space for them.

Should be no functional changes, just a small speedup/less memory use
during subdivision for these cases.

Code review link:
http://codereview.appspot.com/5558058/