set_error(): Handle construction of pyexpat.error exceptions. They

              now carry a 'code' attribute that gives the Expat error
              number.

Added support for additional handlers for Expat 1.95.*, including
XmlDeclHandler, EntityDeclHandler, ElementDeclHandler, and
AttlistDeclHandler.  Associated constants are in the 'model'
sub-object.

Added two new attributes to the parser object: ordered_attributes and
specified_attributes.  These are used to control how attributes are
reported and which attributes are reported.