CSS and style-properties on master

[Christian Hergert <christian hergert me>]

Builder has a complex Vim and emacs keybinding implementation which
relies on GtkWidget style-properties being configurable from CSS. We
need this because we manage a state-machine using CSS selectors and
transitioning between them in a "keybindings agnostic" way requires a
bit of additional information.

This has broken on gtk+ master (since CSS node work). It renders many,
many, many hours of implementing this in the last couple of months unusable.

For now, working and developing Builder requires that we continue to use
the 3.16 branch.

Is there any chance these are coming back? Do I need to go about finding
a new way to implement this? Doing the Vim implementation in CSS has
been a lot easier to manage than custom keybinding modes written in C. I
really would prefer to keep the implementation this way.

https://git.gnome.org/browse/gnome-builder/tree/data/keybindings/vim.css

At least with Builder, this type of break is manageable since we move in
lockstep with Gtk+/GNOME.

-- Christian