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/hmac.rst b/Doc/library/hmac.rst
index 480d0a7..968b7a4 100644
--- a/Doc/library/hmac.rst
+++ b/Doc/library/hmac.rst
@@ -1,4 +1,3 @@
-
:mod:`hmac` --- Keyed-Hashing for Message Authentication
========================================================
@@ -10,6 +9,10 @@
.. versionadded:: 2.2
+**Source code:** :source:`Lib/hmac.py`
+
+--------------
+
This module implements the HMAC algorithm as described by :rfc:`2104`.