Blender Git Loki

Fix T66282: Make Instances Real: Keep Hierarchy option broken with recursive instancing.

Preserving/rebuilding relashionships in recursive instancing was simply
not supported at all, code handling that was assuming a single level of
instancing.

This commit makes the following changes:
* Mixing DupliCollection and DupliVerts/Faces in the recursive chain is
now supported (by using a same GHash in all cases, differences of
persistent_id handling in hashing and comparison is now down inside the
relevant functions).
* When both "keep hierarchy" and "parent" options are enabled, code will
attempt to parent new objects to their version of instancer (instead of
parenting them systematically to the root object). This will preserve
the hierarchy much better.
* Collection is removed from dupli empties that have been made 'real'
(the duplication flag itself was already cleared, but the link to the
instantiated collection was kept).