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/imghdr.rst b/Doc/library/imghdr.rst
index 90a8304..20f789f 100644
--- a/Doc/library/imghdr.rst
+++ b/Doc/library/imghdr.rst
@@ -1,10 +1,12 @@
-
:mod:`imghdr` --- Determine the type of an image
================================================
.. module:: imghdr
:synopsis: Determine the type of image contained in a file or byte stream.
+**Source code:** :source:`Lib/imghdr.py`
+
+--------------
The :mod:`imghdr` module determines the type of image contained in a file or
byte stream.