bpo-34706: Preserve subclassing in inspect.Signature.from_callable (GH-16108) (GH-16113)

https://bugs.python.org/issue34706

Specifically in the case of a class that does not override its
constructor signature inherited from object.

These are Buck Evan @bukzor's changes cherrypicked from GH-9344.
(cherry picked from commit 5b9ff7a0dcb16d6f5c3cd4f1f52e0ca6a4bde586)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
3 files changed