Typeahead Navigation for Nautilus 3.22

Some time ago, I said that I would stop using Nautilus once the typeahead find patch stopped applying. Unfortunately, that day has come. Fortunately, it's Fall Break now, and I managed to set aside some time to figure out what broke with Nautilus THIS time.

I've updated the GitHub Gist with a version of the patch that applies successfully to commit 3fda87baaaae659ceeecc2d00f782f768a6533e9 in the gnome-3-22 branch. Fortunately, the reasons for the patch not applying were not because of some fundamental overhaul of the internal workings of nautilus (hopefully that won't happen anytime soon), but because a bunch of internal variables got renamed around (NautilusWindowSlotDetails became NautilusWindowSlotPrivate, with a whole lot more boilerplate required for accessing essentially the same data. I dunno man).

Given the severe, and worsening, divergence in internal variable nomenclature between the isearch code and the new stuff that's being written, I'd say that the isearch patch is long overdue for some refactoring.

EDIT I was wrong about internal overhauls. New in 3.22: Somehow nautilus_files_view_activate_selection() now causes segfaults when no items are selected (this was not the behaviour in 3.20). This should be properly fixed in nautilus-files-view.c, but I've put in some checking in the isearch functions instead since it's unlikely to get actually fixed upstream (and so that their actually fixing it doesn't cause the patch to fail to apply, just in case).

EDIT II I've merged in the shiny UI stuff from the AUR. I probably should have checked there first before spending an afternoon merging in a patch by hand…