Use a different method to lookup base classes on Jython

Make _get_mro private; Swap logic to put preferred behavior at top level; Update docstring to reference issue.

Jython seems to implement inspect.getmro differently, which causes
any classes with the same name as a class lower in the MRO not to
be returned.

This patch offloads the MRO lookup to a separate function, which
implements different logic for Jython only.

Ref #1024

Rewrite tests to test the actual matching rather than making assertions about the regular expressions. Fixes #1015.

This reverts commit 1955e5b0.

This test is also a regression test for issue #1016.

This reverts commit b50fdf49.

addresses #436: Updating MANIFEST.in does not correctly update the package sdist creates

Docs: notes on setup.cfg and ez_setup

(see # 1006)

Fixes for Visual Studio 2017

- VCRuntimeRedist new path since VS2017.
- Use always last Windows SDK and UCRT SDK when more than one version are available.
- Minors docstrings changes.

Tested with "Visual Studio 2017 Community" and "Visual Studio Build Tools 2017".

Fixes #999: support python_requires and py_modules in configuration files