A consistency patch (Bug 781516)

Hi,

I've prepared a fresher version of Planner's port to Nixpkgs, based on
the master branch and not on the release:

- https://github.com/amiloradovsky/nixpkgs/tree/planner

Please let me know, If there's something to correct before opening the
pull request.

Moreover, I'd like to merge the (one more) patch before that. It's
attached to

- https://bugzilla.gnome.org/show_bug.cgi?id=781516

and I'm not sure if the developers were informed of it's existence or
simply are busy.