Rewrote the docs for supporting cyclic garbage collection to reflect
the new way that once writes types.

Deleted the old section and sample code and added a new section
building on the Noddy example.
diff --git a/Doc/ext/setup.py b/Doc/ext/setup.py
index 5b99cfe..1805b17 100644
--- a/Doc/ext/setup.py
+++ b/Doc/ext/setup.py
@@ -4,5 +4,6 @@
          Extension("noddy", ["noddy.c"]),
          Extension("noddy2", ["noddy2.c"]),
          Extension("noddy3", ["noddy3.c"]),
+         Extension("noddy4", ["noddy4.c"]),
          ])