Add a couple of decrefs to error paths.

Now test_descr only appears to leak two references & I think this
are in fact illusory (it's to do with things getting resurrected in
__del__ methods & it's easy to be believe confusion occurs when that
happens <wink>).  Woohoo!

Objects/intobject.c

@@ -947,12 +947,14 @@ int_subtype_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 		if (!PyLong_Check(tmp)) {
 			PyErr_SetString(PyExc_ValueError,
 					"value must convertable to an int");
+			Py_DECREF(tmp);
 			return NULL;
 		}
 		ival = PyLong_AsLong(tmp);
-		if (ival == -1 && PyErr_Occurred())
+		if (ival == -1 && PyErr_Occurred()) {
+			Py_DECREF(tmp);
 			return NULL;
-
+		}
 	} else {
 		ival = ((PyIntObject *)tmp)->ob_ival;
 	}