- Work around rename of 'copy_reg' -> 'copyreg'.

- Fix deprecated class advice.


- Drop unneeded unicode literals.

Fixed a typo in PWRD.update found by coverage.

It is now examples for the doctests, and no longer a test module.

It is now the canonical test for both C and Python implementations.

It no longer contains tests, only examples to be pickled.

Match its behavior in pyPersistence.

This makes the pure-Python implementation match the C version.

Fix copyright holder per repository policy.

Ensure that Python reference impl. of Timestamp gets tested even if C
impl. builds.

Zap fossil timestamp-manipulation functionss:  they now live in
'persistent.timestamp'.

Drop can't-get-here condition in PickleCache.__delitem__.

Cover PickleCache.debug_info, and fix a bug found thereby.

Drop support for Python < 2.6.