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/abc.rst b/Doc/library/abc.rst
index 0408f30..ef8b08e 100644
--- a/Doc/library/abc.rst
+++ b/Doc/library/abc.rst
@@ -9,6 +9,10 @@
.. versionadded:: 2.6
+**Source code:** :source:`Lib/abc.py`
+
+--------------
+
This module provides the infrastructure for defining :term:`abstract base
classes <abstract base class>` (ABCs) in Python, as outlined in :pep:`3119`; see the PEP for why this
was added to Python. (See also :pep:`3141` and the :mod:`numbers` module