Add a note to Node.isSameNode() that it is based on the DOM Level 3 working

draft.  I'm not sure that's important, but Uche thinks it is.

Doc/lib/xmldom.tex

@@ -242,6 +242,12 @@ Returns true if \var{other} refers to the same node as this node.
 This is especially useful for DOM implementations which use any sort
 of proxy architecture (because more than one object can refer to the
 same node).
+
+\strong{Note:}  This is based on a proposed DOM Level 3 API which is
+still in the ``working draft'' stage, but this particular interface
+appears uncontroversial.  Changes from the W3C will not necessarily
+affect this method in the Python DOM interface (though any new W3C
+API for this would also be supported).
 \end{methoddesc}
 
 \begin{methoddesc}[Node]{appendChild}{newChild}