Issue #13020: Fix a reference leak when allocating a structsequence object fails.

Patch by Suman Saha.

diff --cc Misc/NEWS
index 2f8a5c198b502bccfe833c2cda4df71869667b89,4d3d665e54d43e1db7d51124341dce0914ac9b35..b57cd2146aeb9f5339891236680585a241bdcce3
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,9 -10,9 +10,12 @@@ What's New in Python 3.3 Alpha 1
  Core and Builtins
  -----------------
  
+ - Issue #13020: Fix a reference leak when allocating a structsequence object
+   fails.  Patch by Suman Saha.
+ 
 +- Issue #13777: Add PF_SYSTEM sockets on OS X.
 +  Patch by Michael Goderbauer.
 +
  - Issue #13908: Ready types returned from PyType_FromSpec.
  
  - Issue #11235: Fix OverflowError when trying to import a source file whose