Given it does seem likely Tracker is going to miss the goal to get all
applications ported to Tracker 3, the scenario where there's applications
linking to Tracker 2.x while GTK was built with Tracker 3 support becomes
more likely.
Avoid the upcoming GType clashes if that were the case, and resort to the
good (I lie) old Tracker 2 search engine.
Provide the minimal info necessary. Improves apparent responsiveness
(since we don't visibly clear and repopulate the list) and saves doing
file stat/reads on every file in the result set.
