features in BerkeleyDB not exposed.  notably: the DB_MPOOLFILE interface
has not yet been wrapped in an object.

Adds support for building and installing bsddb3 in python2.3 that has
an older version of this module installed as bsddb without conflicts.
The pybsddb.sf.net build/packaged version of the module uses a
dynamicly loadable module called _pybsddb rather than _bsddb.