Stop producing or using OverflowWarning.  PEP 237 thought this would
happen in 2.3, but nobody noticed it still was getting generated (the
warning was disabled by default).  OverflowWarning and
PyExc_OverflowWarning should be removed for 2.5, and left notes all over
saying so.
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index 1715e97..f433cc0 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -74,6 +74,7 @@
 PyAPI_DATA(PyObject *) PyExc_DeprecationWarning;
 PyAPI_DATA(PyObject *) PyExc_PendingDeprecationWarning;
 PyAPI_DATA(PyObject *) PyExc_SyntaxWarning;
+/* PyExc_OverflowWarning will go away for Python 2.5 */
 PyAPI_DATA(PyObject *) PyExc_OverflowWarning;
 PyAPI_DATA(PyObject *) PyExc_RuntimeWarning;
 PyAPI_DATA(PyObject *) PyExc_FutureWarning;