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/simplexmlrpcserver.rst b/Doc/library/simplexmlrpcserver.rst
index c0819bf..3618728 100644
--- a/Doc/library/simplexmlrpcserver.rst
+++ b/Doc/library/simplexmlrpcserver.rst
@@ -14,6 +14,10 @@
 
 .. versionadded:: 2.2
 
+**Source code:** :source:`Lib/SimpleXMLRPCServer.py`
+
+--------------
+
 The :mod:`SimpleXMLRPCServer` module provides a basic server framework for
 XML-RPC servers written in Python.  Servers can either be free standing, using
 :class:`SimpleXMLRPCServer`, or embedded in a CGI environment, using