A case study in transitive overrides. WebKit needs fresh glib. This means it needs a whole slice of system built against glib-2.22.. Added overrides are generic enough, though. So the same way can be used to override everything. I have failed (so far?) to add mkOverridable into stdenv, though.

svn path=/nixpkgs/trunk/; revision=17661

pkgs/development/libraries/avahi/default.nix

@@ -1,6 +1,6 @@
 { fetchurl, stdenv, pkgconfig, libdaemon, dbus, perl, perlXMLParser
 , expat, gettext, intltool, glib, gtk, qt4 ? null, lib
-, qt4Support ? false }:
+, qt4Support ? false, ...}:
 
 assert qt4Support -> qt4 != null;