Blender Git Loki

Merge branch 'master' into free-refcount-ids

Free IDs; lattice & camera.

Free IDs: images & lamps.

ID freeing: materials and textures.

ID free: tackle Scene (and Library, but not much to do there).

Merge branch 'master' into free-refcount-ids

Clean up `BKE_object_free()` and add `BKE_object_release_datablocks()`.

Similar changed to those done for mesh/curve/mball.

Also, systematically nullify pointers in `_free()` functions, this does not cost
much and can help troubleshooting later.

And tag `BKE_object_unlink()` as an horrible piece of code...

Cleanup of free/unlink/release of ID: mesh/curve/mball.

Renamed their `_unlink()` functions to `_release_datablocks()`, since they do not
unlink anything (not in the sense `BKE_object_unklink()` does, at least)!

Also, added a `const bool do_id_user` to their `_free()`, for consistency, now
relevant `_release_datablocks()` func only gets called when this option is set.