Bug #1599782: Fix segfault on bsddb.db.DB().type().
The problem is that _DB_get_type() can't be called without the GIL
because it calls a bunch of PyErr_* APIs when an error occurs.
There were no other cases in this file that it was called without the GIL.
Removing the BEGIN/END THREAD around _DB_get_type() made everything work.
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.