licenses: Add GNU FDL 1.3+.

* guix/licenses.scm (fdl1.3+): New variable.

guix/licenses.scm

 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2014 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
 ;;; Copyright © 2012, 2013 Nikita Karetnikov <nikita@karetnikov.org>
 ;;;
@@ -31,6 +31,7 @@ (define-module (guix licenses)
             expat
             freetype
             gpl1 gpl1+ gpl2 gpl2+ gpl3 gpl3+
+            fdl1.3+
             isc
             ijg
             ibmpl1.0
@@ -161,6 +162,11 @@ (define gpl3+
            "https://www.gnu.org/licenses/gpl.html"
            "https://www.gnu.org/licenses/license-list#GNUGPLv3"))
 
+(define fdl1.3+
+  (license "FDL 1.3+"
+           "https://www.gnu.org/licenses/fdl.html"
+           "https://www.gnu.org/licenses/license-list#FDL"))
+
 (define isc
   (license "ISC"
            "http://directory.fsf.org/wiki/License:ISC"