[Bf-codereview] Partial Visibility (Sculpt) (issue 5695043)

[NicholasBishop at gmail.com]

Reviewers: bf-codereview_blender.org,

Description:
This patch re-introduces the partial visibility feature for sculpt mode.

If you use git, here is a tar of the individual patches:
http://wiki.blender.org/uploads/c/c9/Partial-visibility-00.tar.bz2

Documentation:
http://wiki.blender.org/index.php/User:Nicholasbishop/PartialVisibility


Please review this at http://codereview.appspot.com/5695043/

Affected files:
   source/blender/blenkernel/BKE_multires.h
   source/blender/blenkernel/BKE_paint.h
   source/blender/blenkernel/BKE_subsurf.h
   source/blender/blenkernel/intern/DerivedMesh.c
   source/blender/blenkernel/intern/cdderivedmesh.c
   source/blender/blenkernel/intern/customdata.c
   source/blender/blenkernel/intern/multires.c
   source/blender/blenkernel/intern/paint.c
   source/blender/blenkernel/intern/subsurf_ccg.c
   source/blender/blenlib/BLI_pbvh.h
   source/blender/blenlib/intern/pbvh.c
   source/blender/blenloader/intern/readfile.c
   source/blender/blenloader/intern/writefile.c
   source/blender/editors/sculpt_paint/CMakeLists.txt
   source/blender/editors/sculpt_paint/paint_hide.c
   source/blender/editors/sculpt_paint/paint_intern.h
   source/blender/editors/sculpt_paint/paint_ops.c
   source/blender/editors/sculpt_paint/sculpt.c
   source/blender/editors/sculpt_paint/sculpt_intern.h
   source/blender/editors/sculpt_paint/sculpt_undo.c
   source/blender/gpu/GPU_buffers.h
   source/blender/gpu/intern/gpu_buffers.c
   source/blender/makesdna/DNA_customdata_types.h
   source/blender/makesdna/DNA_meshdata_types.h
   source/blender/modifiers/intern/MOD_multires.c
   source/blender/windowmanager/intern/wm_operators.c