Backport source links from 3.x.
Existing links have been updated to use the new reST role. In some
files, I have also made cosmetic changes to the header.
diff --git a/Doc/library/dummy_threading.rst b/Doc/library/dummy_threading.rst
index 0ffb687..39ca061 100644
--- a/Doc/library/dummy_threading.rst
+++ b/Doc/library/dummy_threading.rst
@@ -1,10 +1,12 @@
-
:mod:`dummy_threading` --- Drop-in replacement for the :mod:`threading` module
==============================================================================
.. module:: dummy_threading
:synopsis: Drop-in replacement for the threading module.
+**Source code:** :source:`Lib/dummy_threading.py`
+
+--------------
This module provides a duplicate interface to the :mod:`threading` module. It
is meant to be imported when the :mod:`thread` module is not provided on a