Issue here was that py API code was keeping references (pointers) to the
liniked data-blocks, which can actually be duplicated and then deleted
during the 'make local' process...
Would have like to find a better way than passing optional GHash to get
the oldid->newid mapping, but could not think of a better idea.
Uses similar way of storing temp data as object copy paste, just
uses different read entrypoint which does not modify current bmain.
This gives ability to easily copy-paste poses from one blender to
another one.
Hopefully doesn't introduce user-measurable differences.
Request from Peer here in the studio.
Reviewers: mont29
Reviewed By: mont29
Subscribers: hjalti, fsiddi
Differential Revision: https://developer.blender.org/D2229
