org.el: Add version header

* org.el: Add version header.
* README_maintainer: Mention Version header.

README_maintainer

@@ -34,7 +34,8 @@ release.
 
 When doing a /major release/, make sure all changes from the maint
 branch are merged into the the master branch, then merge the master
-branch back into maint to synchronize the two.
+branch back into maint to synchronize the two.  Further, make sure to
+update the Version and Package-Requires headers in org.el.
 
 ** Minor release
 
@@ -42,7 +43,9 @@ The release number for minor releases look like this:  =7.13.1=
 
 Minor releases are small amends to main releases.  Usually they fix
 critical bugs discovered in a main release.  Minor bugs are usually
-not fixed -- they will be adressed in the next main release.
+not fixed -- they will be addressed in the next main release.  Make
+sure to update the Version header in org.el when making a new minor
+release.
 
 Only the fix to the bug is bundled into a release, without the main
 development work going on in the master branch.  Since the bug fix

lisp/org.el

@@ -4,9 +4,11 @@
 ;; Copyright (C) 2004-2015 Free Software Foundation, Inc.
 ;;
 ;; Author: Carsten Dominik <carsten at orgmode dot org>
-;; Maintainer: Carsten Dominik <carsten at orgmode dot org>
+;; Maintainer: Bastien Guerry <bzg at gnu dot org>
+;; URL: http://orgmode.org
+;; Version: 8.3.1
 ;; Keywords: outlines, hypermedia, calendar, wp
-;; Homepage: http://orgmode.org
+;; Package-Requires: ((emacs "23.2"))
 ;;
 ;; This file is part of GNU Emacs.
 ;;