Blender Git Loki

Fix missing pose bone hash table in stub poses of action constraints.

This is a follow-up fix for rBa10b2fe. The Action constraint uses a hackish
stub object and pose, which doesn't have a hash table for fast lookups.
This doesn't seem to be a big issue with the old depsgraph, but in the new
depsgraph it creates a large number of cache misses and significant slowdown,
possibly because of additional threading and less simple bone loops.