Make the classes exposed by threading.py new-style classes.  This is
mostly for convenience and to aid debugging.
diff --git a/Misc/NEWS b/Misc/NEWS
index d3761f9..84da757 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -24,6 +24,9 @@
 Library
 -------
 
+- The classes in threading.py are now new-style classes.  That they
+  weren't before was an oversight.
+
 - SF bug 763023: fix uncaught ZeroDivisionError in difflib ratio methods
   when there are no lines.