Be more clear about the specific rules for supporting the cyclic GC in an extension object.  Also included an example showing exactly what needs to be done and nothing else.
Be more clear about the specific rules for supporting the cyclic GC in an
extension object.  Also included an example showing exactly what needs to
be done and nothing else.

This closes SF bug #228591.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator