The update tracking code was ugly and using deprecated drawing APIs. It
was also in the wrong place.
So instead of trying to keep it working, I'll remove it. We need to find
a better way to put it and make it work there.
The current way of exposing GDK API that should be considered internal
to GTK+ is to append a 'libgtk_only' suffix to the function name; this
is not really safe.
GLib has been using a slightly different approach: a private table of
function pointers, and a macro that allows accessing the desired symbol
inside that vtable.
We can copy the approach, and deprecate the 'libgtk_only' symbols in
lieu of outright removal.
https://bugzilla.gnome.org/show_bug.cgi?id=739781
