Issue #2682: ctypes callback functions no longer contain a cyclic
reference to themselves.

Backport from trunk.
diff --git a/Misc/NEWS b/Misc/NEWS
index d66e26c..e53f02b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -45,6 +45,9 @@
 Library
 -------
 
+- Issue #2682: ctypes callback functions no longer contain a cyclic
+  reference to themselves.
+
 - Issue #2670:  Fix a failure in urllib2.build_opener(), when passed two
   handlers that derive the same default base class.