Update PEP 3100 wrt. __nonzero__ => __bool__ transition.

pep-3100.txt

@@ -108,6 +108,9 @@ Core language
   There's no literal for an empty set; use set() (or {1}&{2} :-).
   There's no frozenset literal; they are too rarely needed.
 * Might reconsider PEP 299 [30]_: special __main__() function in modules.
+* The ``__nonzero__`` special method will be renamed to ``__bool__``
+  and have to return a bool. The typeobject slot will be called
+  ``tp_bool`` [32]_ [done]
 
 To be removed:
 
@@ -337,6 +340,9 @@ References
 .. [31] SF patch "sys.id() and sys.intern()"
    http://www.python.org/sf/1601678
 
+.. [32] python-3000 email ("__nonzero__ vs. __bool__")
+   http://mail.python.org/pipermail/python-3000/2006-November/004524.html
+
 .. [#pep328] PEP 328 (Imports: Multi-Line and Absolute/Relative)
    http://www.python.org/dev/peps/pep-0328