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/dis.rst b/Doc/library/dis.rst
index 9addfe7..8dee901 100644
--- a/Doc/library/dis.rst
+++ b/Doc/library/dis.rst
@@ -1,21 +1,18 @@
-
 :mod:`dis` --- Disassembler for Python bytecode
 ===============================================
 
 .. module:: dis
    :synopsis: Disassembler for Python bytecode.
 
+**Source code:** :source:`Lib/dis.py`
+
+--------------
 
 The :mod:`dis` module supports the analysis of CPython :term:`bytecode` by
 disassembling it. The CPython bytecode which this module takes as an
 input is defined in the file :file:`Include/opcode.h` and used by the compiler
 and the interpreter.
 
-.. seealso::
-
-   Latest version of the `dis module Python source code
-   <http://svn.python.org/view/python/branches/release27-maint/Lib/dis.py?view=markup>`_
-
 .. impl-detail::
 
    Bytecode is an implementation detail of the CPython interpreter!  No