Add a few missing source links from 2.7 and harmonize lib docs headers
diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 3f9ec0b..2443180 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -4,6 +4,9 @@
 .. module:: string
    :synopsis: Common string operations.
 
+**Source code:** :source:`Lib/string.py`
+
+--------------
 
 .. seealso::
 
@@ -11,10 +14,6 @@
 
    :ref:`string-methods`
 
-**Source code:** :source:`Lib/string.py`
-
---------------
-
 String constants
 ----------------