gnu: Add libpng-1.2.

* gnu/packages/image.scm (libpng-1.2): New variable.

gnu/packages/image.scm

@@ -2,7 +2,7 @@
 ;;; Copyright © 2013, 2015, 2016 Andreas Enge <andreas@enge.fr>
 ;;; Copyright © 2014, 2015, 2016 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2014, 2015 Alex Kost <alezost@gmail.com>
-;;; Copyright © 2014 Ricardo Wurmus <rekado@elephly.net>
+;;; Copyright © 2014, 2016 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2015 Taylan Ulrich Bayırlı/Kammer <taylanbayirli@gmail.com>
 ;;; Copyright © 2015 Amirouche Boubekki <amirouche@hypermove.net>
 ;;; Copyright © 2014 John Darrington <jmd@gnu.org>
@@ -76,6 +76,22 @@ library.  It supports almost all PNG features and is extensible.")
    (license license:zlib)
    (home-page "http://www.libpng.org/pub/png/libpng.html")))
 
+(define-public libpng-1.2
+  (package
+    (inherit libpng)
+    (version "1.2.56")
+    (source
+     (origin
+       (method url-fetch)
+       ;; Note: upstream removes older tarballs.
+       (uri (list (string-append "mirror://sourceforge/libpng/libpng12/"
+                                 version "/libpng-" version ".tar.xz")
+                  (string-append
+                   "ftp://ftp.simplesystems.org/pub/libpng/png/src"
+                   "/libpng12/libpng-" version ".tar.xz")))
+       (sha256
+        (base32 "1ghd03p353x0vi4dk83n1nlldg11w7vqdk3f99rkgfb82ic59ki4"))))))
+
 (define-public libjpeg
   (package
    (name "libjpeg")