Merge: #17476: make allmethods actually return all methods.

This fixes a regression relative to Python2.  (In 2, methods on a class were
unbound methods and matched the inspect queries being done, in 3 they are just
functions and so were missed).

This is an undocumented function that pydoc itself does not use, but
I found that numpy at least uses it in its documentation generator.

Original patch by Matt Bachmann.