* Now uses the CCG DerivedMesh also in object mode, used to be edit mode only.
* Create CD_ORIGINDEX layer on demand, to save memory.
* Removed ss_to_cdderivedmesh function, and instead create ccgdm and then
convert that to cddm, to avoid code duplication.
* Added and implement DerivedMesh interface functions to obtain face grids.
* Store edge/face flags more memory efficient.
* Export CCGDerivedMesh struct in BKE_subsurf.h