Blender Git Loki

Armature: implement universal hash table lookup of Bone objects by name.

Since drivers on Bone properties are really supposed to be stored
in Armature data and access bones via its bones[] collection, this
lookup path should work efficiently.

Mass lookup of bones by name was already done through hashes,
but they were built temporarily every time that was needed. This
simply replaces it with a common hash table computed immediately
after file load, copy, or Edit to Object mode switch.