Add a new warning gategory, ResourceWarning, as discussed on python-dev.  It is silent by default,
except when configured --with-pydebug.

Emit this warning from the GC shutdown procedure, rather than just printing to stderr.
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index 58a3df7..25843c3 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -170,6 +170,7 @@
 PyAPI_DATA(PyObject *) PyExc_ImportWarning;
 PyAPI_DATA(PyObject *) PyExc_UnicodeWarning;
 PyAPI_DATA(PyObject *) PyExc_BytesWarning;
+PyAPI_DATA(PyObject *) PyExc_ResourceWarning;
 
 
 /* Convenience functions */