Issue #3660 (part of): fix a memory leak in _pickle.

Patch by Amaury Forgeot d'Arc, review by me.
diff --git a/Misc/NEWS b/Misc/NEWS
index 889cead..1bb4f6f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -80,6 +80,8 @@
 Library
 -------
 
+- Issue #3660: fix a memory leak in the C accelerator of the pickle module.
+
 - Issue #3160: the "bdist_wininst" distutils command didn't work.
 
 - Issue #1658: tkinter changes dict size during iteration in both