wrong type of database in dbshelve.
* fix a typo in the exception name when checking args

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.

doesn't have UserDict.DictMixin.

   to have a full dictionary interface.

so merge from the bsddb-bsddb3-schizo-branch back to the trunk.

version 4.1.1 and works with up to BerkeleyDB 4.1.25.