Issue #9630: Redecode filenames when setting the filesystem encoding

Redecode the filenames of:

 - all modules: __file__ and __path__ attributes
 - all code objects: co_filename attribute
 - sys.path
 - sys.meta_path
 - sys.executable
 - sys.path_importer_cache (keys)

Keep weak references to all code objects until initfsencoding() is called, to
be able to redecode co_filename attribute of all code objects.
diff --git a/Include/code.h b/Include/code.h
index f0f88cd..bdbfaba 100644
--- a/Include/code.h
+++ b/Include/code.h
@@ -99,6 +99,13 @@
 PyAPI_FUNC(PyObject*) PyCode_Optimize(PyObject *code, PyObject* consts,
                                       PyObject *names, PyObject *lineno_obj);
 
+/* List of weak references to all code objects. The list is used by
+   initfsencoding() to redecode code filenames at startup if the filesystem
+   encoding changes. At initfsencoding() exit, the list is set to NULL and it
+   is no more used. */
+
+extern PyObject *_Py_code_object_list;
+
 #ifdef __cplusplus
 }
 #endif