- some of the refinements from the sa_synonyms branch which will

- some of the refinements from the sa_synonyms branch which will
allow the hybrid extension to work, but doesn't re-implement synonym,
comparable_property,concreteinheritedproperty
- mapper.get_property() and _entity_descriptor use plain getattr()
to get at descriptors in all cases, thereby placing more
trust in the ultimate class-bound attribute to provide mapped
properties