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/pipes.rst b/Doc/library/pipes.rst
index 1f2b2ff..016a720 100644
--- a/Doc/library/pipes.rst
+++ b/Doc/library/pipes.rst
@@ -1,4 +1,3 @@
-
 :mod:`pipes` --- Interface to shell pipelines
 =============================================
 
@@ -7,6 +6,9 @@
    :synopsis: A Python interface to Unix shell pipelines.
 .. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
 
+**Source code:** :source:`Lib/pipes.py`
+
+--------------
 
 The :mod:`pipes` module defines a class to abstract the concept of a *pipeline*
 --- a sequence of converters from one file to  another.