Blender Git Loki

Tweaks to RNA for GPencil pointers

Some tweaks to the RNA for Grease Pencil data pointers in an attempt to get
these editable via the Outliner datablocks view. It seems though that pointer
editing there is broken everywhere instead. Nevertheless, these tweaks should
make this handling more correct (i.e. refcounts are used accordingly).

For now, the best way of setting Grease Pencil data on objects, etc. is to do
so using Python