[Checkins] [zopefoundation/persistent] 9e4c4c: Incorporate review feedback.

[Jason Madden]

  Branch: refs/heads/issue131
  Home:   https://github.com/zopefoundation/persistent
  Commit: 9e4c4c0b7dc24653064d41cbaa8577974802d5e0
      https://github.com/zopefoundation/persistent/commit/9e4c4c0b7dc24653064d41cbaa8577974802d5e0
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2020-03-03 (Tue, 03 Mar 2020)

  Changed paths:
    M CHANGES.rst
    M persistent/__init__.py
    M persistent/_compat.py
    M persistent/interfaces.py
    M persistent/persistence.py
    M persistent/picklecache.py
    A persistent/tests/test__compat.py
    M persistent/tests/test_persistence.py
    M persistent/tests/test_picklecache.py
    M persistent/tests/test_timestamp.py
    M persistent/timestamp.py

  Log Message:
  -----------
  Incorporate review feedback.

- Let an empty value of PURE_PYTHON mean the same thing as it did before (no preference)
- Add tests for the functions that handle PURE_PYTHON
- Clean up imports in various places
- Add more tests for C TimeStamp hash code.
- Add some comments.