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/quopri.rst b/Doc/library/quopri.rst
index 87d70c3..67cbaba 100644
--- a/Doc/library/quopri.rst
+++ b/Doc/library/quopri.rst
@@ -1,4 +1,3 @@
-
 :mod:`quopri` --- Encode and decode MIME quoted-printable data
 ==============================================================
 
@@ -10,6 +9,10 @@
    pair: quoted-printable; encoding
    single: MIME; quoted-printable encoding
 
+**Source code:** :source:`Lib/quopri.py`
+
+--------------
+
 This module performs quoted-printable transport encoding and decoding, as
 defined in :rfc:`1521`: "MIME (Multipurpose Internet Mail Extensions) Part One:
 Mechanisms for Specifying and Describing the Format of Internet Message Bodies".
@@ -18,11 +21,6 @@
 :mod:`base64` module is more compact if there are many such characters, as when
 sending a graphics file.
 
-.. seealso::
-
-   Latest version of the `quopri module Python source code
-   <http://svn.python.org/view/python/branches/release27-maint/Lib/quopri.py?view=markup>`_
-
 .. function:: decode(input, output[,header])
 
    Decode the contents of the *input* file and write the resulting decoded binary