3.1.6 (unstable):

Gtk:
* All H* or V* specialized classes have been deprecated, to 
  match the deprecations in the GTK+ C API. You should now 
  set the orientation instead.
  This includes HBox, VBox, HButtonBox, VButtonBox, HPaned, VPaned, HScale, 
  VScale,  HSeparator, VSeparator, HScrollbar and VScrollbar.
  HBox and VBox are not protected by ifdefs because they are used as base 
  classes for several other widgets, and we can't change that without breaking 
  ABI.
* Dialog: Deprecate get_vbox(), replacing with get_content_area(), 
  to match the C function name.