pan: sha1 -> sha256

pkgs/applications/networking/newsreaders/pan/default.nix

···
 
   src = fetchurl {
     url = "http://pan.rebelbase.com/download/releases/${version}/source/pan-${version}.tar.bz2";
-    sha1 = "01ea0361a6d81489888e6abb075fd552999c3c60";
+    sha256 = "1fab2i6ngqp66lhls0g7j8d1c1rk75afiqr3r1x2sn3zk47k4pxz";
   };
 
   buildInputs = [ pkgconfig gtk2 perl gmime gettext intltool dbus_glib libnotify ]