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/pyclbr.rst b/Doc/library/pyclbr.rst
index dd6c0ae..2f81451 100644
--- a/Doc/library/pyclbr.rst
+++ b/Doc/library/pyclbr.rst
@@ -1,4 +1,3 @@
-
 :mod:`pyclbr` --- Python class browser support
 ==============================================
 
@@ -6,6 +5,9 @@
    :synopsis: Supports information extraction for a Python class browser.
 .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
 
+**Source code:** :source:`Lib/pyclbr.py`
+
+--------------
 
 The :mod:`pyclbr` module can be used to determine some limited information
 about the classes, methods and top-level functions defined in a module.  The