range/spinbutton changes

[Havoc Pennington <hp redhat com>]

Hi,

For GtkScale and GtkSpinButton, I think we should allow people to use
these widgets without touching GtkAdjustment. GtkAdjustment makes them
a good bit harder to use and learn (model-view is just total overkill
for these little widgets).

Proposed API additions:

 set_range ():
   set_range (spinbutton, min, max, climbrate)
   set_range (scale, min, max, small_step, page_step);
 
 get_range():
   for symmetry

 "changed" signal: 
    just value_changed on the adjustment

 constructors that take the set_range() arguments instead of 
  an adjustment  

Also, for GtkRange, add set_value and get_value as with SpinButton. 

Havoc