On my machines the test suite complains that a couple of the
restraints defined in python are missing the virtual functions for
version and last_modified_by. This patch adds those.
On a separate note, it is not clear to me that anyone will ever bother
to actually update these fields. Especially since they are defined
primarily in the headers and code changes are most likely to occur in
the .cpp files. Is it possible to use a SVN hook to update them
automatically?