correct ontosys url - closes 1167329

Doc/lib/libxmlrpclib.tex

@@ -32,7 +32,7 @@ the Python constant \code{None} will be translated into XML; the
 default behaviour is for \code{None} to raise a \exception{TypeError}.
 This is a commonly-used extension to the XML-RPC specification, but isn't
 supported by all clients and servers; see
-\url{http://ontosys.com/xml-rpc/extensions.html} for a description. 
+\url{http://ontosys.com/xml-rpc/extensions.php} for a description. 
 
 Both the HTTP and HTTPS transports support the URL syntax extension for
 HTTP Basic Authentication: \code{http://user:pass@host:port/path}.  The