ed: Add fedoraproject mirror.

The existing URL has gone dark; this commit adds one from fedoraproject.org
that still works. We put the new mirror first since ed is in the bootstrap
path, and 16.09 bootstrap doesn't try later URLs.

pkgs/applications/editors/ed/default.nix

@@ -2,14 +2,18 @@
 
 stdenv.mkDerivation rec {
   name = "ed-1.13";
+  file_md5 = "fb8ffc8d8072e13dd5799131e889bfa5"; # for fedora mirror
 
   src = fetchurl {
     # gnu only provides *.lz tarball, which is unfriendly for stdenv bootstrapping
     #url = "mirror://gnu/ed/${name}.tar.gz";
     # When updating, please make sure the sources pulled match those upstream by
     # Unpacking both tarballs and running `find . -type f -exec sha256sum \{\} \; | sha256sum`
     # in the resulting directory
-    url = "http://fossies.org/linux/privat/${name}.tar.bz2";
+    urls = [
+      "http://pkgs.fedoraproject.org/repo/extras/ed/${name}.tar.bz2/${file_md5}/${name}.tar.bz2"
+      "http://fossies.org/linux/privat/${name}.tar.bz2"
+    ];
     sha256 = "1iym2fsamxr886l3sz8lqzgf00bip5cr0aly8jp04f89kf5mvl0j";
   };