stack: rename unstable -> orphan
That's the only instability stack can currently show, but it's about to show
more and showing "unstable" for one type of instability just isn't good.
This software was downloaded from
https://www.mercurial-scm.org/repo/evolve/
Copyright 2011 Peter Arrenbrecht <peter.arrenbrecht@gmail.com>
Logilab SA <contact@logilab.fr>
Pierre-Yves David <pierre-yves.david@ens-lyon.org>
Patrick Mezard <patrick@mezard.eu>
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On Debian systems, the complete text of the GNU General Public License version
2 can be found in `/usr/share/common-licenses/GPL-2'.