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_thread.rst b/Doc/library/dummy_thread.rst
index 5d89760..a4dba86 100644
--- a/Doc/library/dummy_thread.rst
+++ b/Doc/library/dummy_thread.rst
@@ -10,6 +10,9 @@
converting your sources to 3.0; however, you should consider using the
high-lever :mod:`dummy_threading` module instead.
+**Source code:** :source:`Lib/dummy_thread.py`
+
+--------------
This module provides a duplicate interface to the :mod:`thread` module. It is
meant to be imported when the :mod:`thread` module is not provided on a