Add link to Fredrik Lundh's scanner.

pep-0353.txt

@@ -167,6 +167,11 @@ they need all be checked for s# and t# converters, and
 PY_SIZE_T_CLEAN must be defined before including Python.h
 if the calls have been updated accordingly.
 
+Fredrik Lundh has written a scanner_ which checks the code
+of a C module for usage of APIs whose signature has changed.
+
+.. _scanner: http://svn.effbot.python-hosting.com/stuff/sandbox/python/ssizecheck.py
+
 
 Discussion
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