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/heapq.rst b/Doc/library/heapq.rst
index fcaf28d..86be3bd 100644
--- a/Doc/library/heapq.rst
+++ b/Doc/library/heapq.rst
@@ -10,14 +10,13 @@
 
 .. versionadded:: 2.3
 
+**Source code:** :source:`Lib/heapq.py`
+
+--------------
+
 This module provides an implementation of the heap queue algorithm, also known
 as the priority queue algorithm.
 
-.. seealso::
-
-   Latest version of the `heapq Python source code
-   <http://svn.python.org/view/*checkout*/python/branches/release27-maint/Lib/heapq.py?content-type=text%2Fplain>`_
-
 Heaps are binary trees for which every parent node has a value less than or
 equal to any of its children.  This implementation uses arrays for which
 ``heap[k] <= heap[2*k+1]`` and ``heap[k] <= heap[2*k+2]`` for all *k*, counting