Make WebKit use libsoup 2.31.2 via deepOverride. Edit a few packages that were overridable but did not allow extra arguments. Remove a catch with deepOverride that pkgs.lib had this attribute in a different sense.

svn path=/nixpkgs/trunk/; revision=22529

pkgs/development/interpreters/python/2.6/default.nix

@@ -11,6 +11,7 @@
 , arch ? null
 , sw_vers ? null
 , ncurses ? null
+, ...
 }:
 
 assert zlibSupport -> zlib != null;