gtk: fix warning when finalizing a GtkToolbar
gtk: fix warning when finalizing a GtkToolbar

Move destruction of child widgets from finalize() to dispose()
because unparenting emits a signal with old_parent as object
parameter, which tries to ref the toolbar that is being
finalized.

johne53/MB3Gtk-2,johne53/MB3Gtk-2,Unity-Technologies/gtk,Unity-Technologies/gtk,Distrotech/gtk,Distrotech/gtk,Distrotech/gtk,johne53/MB3Gtk-2,Unity-Technologies/gtk,Distrotech/gtk,Unity-Technologies/gtk,johne53/MB3Gtk-2,Distrotech/gtk,johne53/MB3Gtk-2,Unity-Technologies/gtk