Updated documentation to:

- point out the importance of reassigning data members before
  assigning thier values

- correct my missconception about return values from visitprocs. Sigh.

- mention the labor saving Py_VISIT and Py_CLEAR macros.
diff --git a/Doc/ext/noddy2.c b/Doc/ext/noddy2.c
index 03fe288..2683e8b 100644
--- a/Doc/ext/noddy2.c
+++ b/Doc/ext/noddy2.c
@@ -46,7 +46,7 @@
 static int
 Noddy_init(Noddy *self, PyObject *args, PyObject *kwds)
 {
-    PyObject *first=NULL, *last=NULL;
+    PyObject *first=NULL, *last=NULL, *tmp;
 
     static char *kwlist[] = {"first", "last", "number", NULL};
 
@@ -56,15 +56,17 @@
         return -1; 
 
     if (first) {
-        Py_XDECREF(self->first);
+        tmp = self->first;
         Py_INCREF(first);
         self->first = first;
+        Py_XDECREF(tmp);
     }
 
     if (last) {
-        Py_XDECREF(self->last);
+        tmp = self->last;
         Py_INCREF(last);
         self->last = last;
+        Py_XDECREF(tmp);
     }
 
     return 0;