Issue7186: document that __doc__ is not inherited by subclasses

--HG--
branch : 3.4
Issue7186: document that __doc__ is not inherited by subclasses
Issue #20155: Fix non-buildbot test failure on Windows.  Patch by Claudiu Popa,
revised by R. David Murray.

--HG--
branch : 3.4
Merge with 3.4
Issue20689: add missing API pieces to __all__

--HG--
branch : 3.4
Issue20689: add missing API pieces to __all__