Blender Git Loki

Fix crash happening in Cycles fcurve modifier

Summary:
Crash was happening because of fcurve modifier stack
used modifier's DNA to store temporary data.

Now made it so storage for such a thing is being
allocated locally per object update so multiple objects
which shares the same animation wouldn't run into
threading conflict anymore.

This storage might be a part of EvaluationContext,
but that'd mean passing this context all over in
object_where_is which will clutter API for now without
actual benefit for this.

Optimization notes: storage is only being allocated
if there're Cycles modifier in the stack, so there're
no extra allocations happening in all other cases.

To make code a bit less cluttered with this storage
passing all over the place added extra callbacks to
the FModifier storage which runs evaluation with the
given storage.

Reviewers: brecht, campbellbarton, aligorith

CC: plasmasolutions

Differential Revision: https://developer.blender.org/D147