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/keyword.rst b/Doc/library/keyword.rst
index 3b69d0b..173db23 100644
--- a/Doc/library/keyword.rst
+++ b/Doc/library/keyword.rst
@@ -1,10 +1,12 @@
-
 :mod:`keyword` --- Testing for Python keywords
 ==============================================
 
 .. module:: keyword
    :synopsis: Test whether a string is a keyword in Python.
 
+**Source code:** :source:`Lib/keyword.py`
+
+--------------
 
 This module allows a Python program to determine if a string is a keyword.
 
@@ -19,9 +21,3 @@
    Sequence containing all the keywords defined for the interpreter.  If any
    keywords are defined to only be active when particular :mod:`__future__`
    statements are in effect, these will be included as well.
-
-
-.. seealso::
-
-   Latest version of the `keyword module Python source code
-   <http://svn.python.org/view/python/branches/release27-maint/Lib/keyword.py?view=markup>`_