gtk-style-context has landed

[Carlos Garnacho <carlosg gnome org>]

Hey :),

I have just merged the gtk-style-context branch in master, here's the
status of things:

      * The new API is fully functional, well documented, and used
        underneath GtkStyle, a few widgets are using it directly
        already.
      * GtkStyle and GtkRcStyle are deprecated, but more code can be
        surely removed, the most tricky bit might be
        GtkRcPropertyParser, which is used in GtkSettings, although we
        can likely just typedef it to GtkSettingsParser.
      * Widgets in gtk/ need to use GtkStyleContext directly shortly,
        during the transition there might be visual glitches as widgets
        expose further information themeable through CSS, the builtin
        one will be kept as sane as possible though.
      * Apps are encouraged to switch, I guess a GNOME goal should be
        set up to handle this, Javier? :)

I'll be handling these items during the next days, helping hands are of
course welcome.

Cheers,
  Carlos