Use locale encoding if Py_FileSystemDefaultEncoding is not set

 * PyUnicode_EncodeFSDefault(), PyUnicode_DecodeFSDefaultAndSize() and
   PyUnicode_DecodeFSDefault() use the locale encoding instead of UTF-8 if
   Py_FileSystemDefaultEncoding is NULL
 * redecode_filenames() functions and _Py_code_object_list (issue #9630)
   are no more needed: remove them
diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
index 39a6b2e..f61712b 100644
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -1193,7 +1193,8 @@
 /* Decode a null-terminated string using Py_FileSystemDefaultEncoding
    and the "surrogateescape" error handler.
 
-   If Py_FileSystemDefaultEncoding is not set, fall back to UTF-8.
+   If Py_FileSystemDefaultEncoding is not set, fall back to the locale
+   encoding.
 
    Use PyUnicode_DecodeFSDefaultAndSize() if the string length is known.
 */
@@ -1205,7 +1206,8 @@
 /* Decode a string using Py_FileSystemDefaultEncoding
    and the "surrogateescape" error handler.
 
-   If Py_FileSystemDefaultEncoding is not set, fall back to UTF-8.
+   If Py_FileSystemDefaultEncoding is not set, fall back to the locale
+   encoding.
 */
 
 PyAPI_FUNC(PyObject*) PyUnicode_DecodeFSDefaultAndSize(
@@ -1216,7 +1218,8 @@
 /* Encode a Unicode object to Py_FileSystemDefaultEncoding with the
    "surrogateescape" error handler, and return bytes.
 
-   If Py_FileSystemDefaultEncoding is not set, fall back to UTF-8.
+   If Py_FileSystemDefaultEncoding is not set, fall back to the locale
+   encoding.
 */
 
 PyAPI_FUNC(PyObject*) PyUnicode_EncodeFSDefault(