DAG node already has got type field, so we could just check whether
type is ID_OB to distinguish whether object_handle_update need to
be called for node->ob.
This saves iterating via scene's bases when preparing threaded
update. This also will very much likely update objects which are
not in the scene base are used in dupli groups.
So now objects form dupli_groups are likely already properly updated
white traversing the DAG with threaded update and special hacks
are needed from main thread to update objects from dupli_groups
which was added in previous commit.
However, kept this hack for a while, need some more thoughts
and investigation.
f49e441927