[Python-Dev] New methods for weakref.Weak*Dictionary types

I'd like to commit this for Python 2.5: http://www.python.org/sf/1479988 The WeakKeyDictionary and WeakValueDictionary don't provide any API to get just the weakrefs out, instead of the usual mapping API. This can be desirable when you want to get a list of everything without creating new references to the underlying objects at that moment. This patch adds methods to make the references themselves accessible using the API, avoiding requiring client code to have to depend on the implementation. The WeakKeyDictionary gains the .iterkeyrefs() and .keyrefs() methods, and the WeakValueDictionary gains the .itervaluerefs() and .valuerefs() methods. The patch includes tests and docs. -Fred -- Fred L. Drake, Jr. <fdrake at acm.org>