This doesn't have a lot of visible effect on standalone ZODB use, but
is important for Zope 2.8.

Here are checkin msgs from the branch relating to ZODB code:

    r29872 | jim | 2005-04-04 07:04:39 -0400 (Mon, 04 Apr 2005) | 3 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/ZODB/serialize.py

    For instances of persistent classes, save a class-module/clas-name
    tuple if the class has a non-empty module string.

    ------------------------------------------------------------------------
    r29871 | jim | 2005-04-04 07:04:33 -0400 (Mon, 04 Apr 2005) | 6 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/ZODB/Connection.py

    Changed sub-transaction abort code to not invalidate created objects.
    There's really no point, because created objects will be unreachable
    after invalidating old objects.  Also, if a created object is
    non-ghostifiable, it will try to load it's state again, and then
    either it would fail or it would load non-committed state.

    ------------------------------------------------------------------------
    r29870 | jim | 2005-04-04 07:04:27 -0400 (Mon, 04 Apr 2005) | 3 lines
    Changed paths:
       A /Zope/branches/jim-fix-zclasses/lib/python/ZODB/persistentclass.py
       A /Zope/branches/jim-fix-zclasses/lib/python/ZODB/persistentclass.txt
       A /Zope/branches/jim-fix-zclasses/lib/python/ZODB/tests/testpersistentclass.py

    Added ZClass-independent test of (and possible base class for)
    persistent-class support machinery.

    ------------------------------------------------------------------------
    r29867 | jim | 2005-04-04 07:03:48 -0400 (Mon, 04 Apr 2005) | 2 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/transaction/_manager.py

    Added missing arguments to commit and abort.

    ------------------------------------------------------------------------
    r29774 | jim | 2005-04-01 06:24:27 -0500 (Fri, 01 Apr 2005) | 3 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/transaction/__init__.py

    Changed to use methods of a threaded manager directly, rather than
    through wrapper functions.

    ------------------------------------------------------------------------
    r29773 | jim | 2005-04-01 06:24:25 -0500 (Fri, 01 Apr 2005) | 3 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/transaction/_manager.py

    Added commit and abort methods to transaction managers.
    This makes direcr use of managers simpler.

    ------------------------------------------------------------------------
    r29101 | jim | 2005-02-10 07:44:52 -0500 (Thu, 10 Feb 2005) | 2 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/ZODB/Connection.py

    Removed an unused attribute.

    ------------------------------------------------------------------------
    r29100 | jim | 2005-02-10 07:42:35 -0500 (Thu, 10 Feb 2005) | 3 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/transaction/_transaction.py

    Changed an XXX comment to an ordinary comment, explaining the relevent
    issue.

    ------------------------------------------------------------------------
    r29099 | jim | 2005-02-10 07:41:58 -0500 (Thu, 10 Feb 2005) | 3 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/ZODB/Connection.py

    Changed some XXX comments to ordinary comments explaining the relevent
    issues.

    ------------------------------------------------------------------------
    r29071 | jim | 2005-02-07 07:36:05 -0500 (Mon, 07 Feb 2005) | 3 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/transaction/_transaction.py

    Added a sanity check to avoid registration of objects without a
    manager. (Perhaps this should be an assert.)

    ------------------------------------------------------------------------
    r29067 | jim | 2005-02-07 07:35:56 -0500 (Mon, 07 Feb 2005) | 15 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/ZODB/Connection.py

    Changed the strategy for handling invalidation of classes.
    No-longer use setklassstate.  Instead, just call _p_invalidate, as
    with any other object.  This changes didn't break any tests, so I
    assume that this was untested. :(

    Changed the strategy for invalidating objects.  Non-ghostifiable
    objects will load their state when they are invalidated.  We have to
    worry about other invalidations that come in while this is happening.
    See the comment in _flush_invalidations.

    We need to force all invalidations to take this into account, by going
    through _flush_invalidations.  I haven't done this yet, but I have
    left some XXX comments in places where it needs to be done to remind
    myself that this needs to be done.

    ------------------------------------------------------------------------
    r29066 | jim | 2005-02-07 07:35:54 -0500 (Mon, 07 Feb 2005) | 8 lines
    Changed paths:
       M /Zope/branches/jim-fix-zclasses/lib/python/persistent/cPickleCache.c

    Changed the strategy for handling invalidation of classes.
    No-longer use setklassstate.  Instead, just call _p_invalidate, as
    with any other object.  This changes didn't break any tests, so I
    assume that this was untested. :(

    Change invalidation to not swallow errors. (Swallowing errors here was a
    travesty!)