Make sure `RetrieveStatus(string)` correctly reports typechanges

[ethomson]

There's some question in #411 that we may or may not correctly get TypeChange results from RetrieveStatus. Let's have some unit tests that validate that this is correct.

[ethomson]

In fact we never ask for typechanges, #411 was requesting new feature work, not reporting a bug. Suggest we drop the stabilization here, treat typechange records from status / diff as a new feature and prioritize it accordingly.