[Checkins] [zopefoundation/zope.interface] f4b777: Make Interface.getTaggedValue follow the __iro__.

[Jason Madden]

  Branch: refs/heads/issue190
  Home:   https://github.com/zopefoundation/zope.interface
  Commit: f4b777d4a52f69aa2cbd79b285320e9c9f5726e9
      https://github.com/zopefoundation/zope.interface/commit/f4b777d4a52f69aa2cbd79b285320e9c9f5726e9
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2020-03-18 (Wed, 18 Mar 2020)

  Changed paths:
    M CHANGES.rst
    M docs/README.rst
    M docs/api/declarations.rst
    M docs/api/specifications.rst
    M src/zope/interface/interface.py
    M src/zope/interface/interfaces.py
    M src/zope/interface/tests/test_interface.py

  Log Message:
  -----------
  Make Interface.getTaggedValue follow the __iro__.

Previously it manually walked up __bases__, meaning the answers could be inconsistent.

Fixes #190.

Also fixes several minor issues in the documentation, mostly cross-reference related.