Make author order tests more strict.

Use varying dates in the test messages to test the order authors are
listed in.  Add tests with repeated author names and unusual date
ordering.  Most of these are broken at the moment, but will be fixed
shortly.

Edited-by: Carl Worth <cworth@cworth.org>: Also update the expected
results for existing emacs tests that currently codify the incorrect
author ordering, (and similarly note them as broken in the current
test suite).