See #490 discussion.
This reverts commit 1278859d31, reversing
changes made to 0c020c98f9.
Conflicts:
pkgs/desktops/xfce/core/xfce4-session.nix (take master)
pkgs/lib/misc.nix (auto)
./JustNothing/.. )+"/"+args.version+".nix")))' hack, you can also just
write `import (./path/to/pkg + "/${version}.nix)'.
svn path=/nixpkgs/trunk/; revision=9792