* gtk/gtkrange.[ch]: implement the GtkOrientable interface. Add
evil code that makes sure that the stepper_detail and slider_detail
set in GtkRangeClass continue to work with the hacked subclasses
below.
* gtk/gtkscale.[ch]: swallow all code from GtkHScale and GtkVScale
and add gtk_scale_new() and gtk_scale_new_with_range() which take
a GtkOrientation argument. Set slider_detail to "Xscale" so above
evil code works.
* gtk/gtkscrollbar.[ch]: add gtk_scrollbar_new() which takes a
GtkOrientation argument. Set stepper_detail to "Xscrollbar" so
above evil code works.
* gtk/gtkhscale.c
* gtk/gtkvscale.c
* gtk/gtkhscrollbar.c
* gtk/gtkvscrollbar.c: remove all code except the constructor and
call gtk_orientable_set_orientation() in init().