Add internal routine _PyModule_Clear(), which does approximately what clear_carefully() used to do in import.c. Differences: leave only __builtins__ alone in the 2nd pass; and don't clear the dictionary (on the theory that as long as there are references left to the dictionary, those might be destructors that might expect __builtins__ to be alive when they run; and __builtins__ can't normally be part of a cycle).

--- a/Include/moduleobject.h	Thu Feb 19 20:50:52 1998 +0000
+++ b/Include/moduleobject.h	Thu Feb 19 20:51:52 1998 +0000
@@ -44,6 +44,7 @@
 extern PyObject *PyModule_New Py_PROTO((char *));
 extern PyObject *PyModule_GetDict Py_PROTO((PyObject *));
 extern char *PyModule_GetName Py_PROTO((PyObject *));
+extern void _PyModule_Clear Py_PROTO((PyObject *));
 
 #ifdef __cplusplus
 }