Log Message:
-----------
Postgres.Object and others no longer depend on this as a base type.
Removed Files:
-------------
be/src:
datum.c
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/datum.c)
datum.h
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/datum.h)