This patch corrects a bug (or modify a feature, it depends of your
pov :)) in the range widgets (scale and scrollbar).

  The default behaviour when you click on the background of a range 
widget (ie not on arrows or the slider) and keep the mouse button 
pressed is to make the slider move in the original direction, even 
if it's not the good direction anymore (the slider's gone too far).

Now the slider go in the direction of the mouse pointer and can stop
if the mouse pointer is on the slider. If you move the mouse (with
the button still pressed) the slider will go in the direction of the
mouse pointer even if it's now the opposite direction.

The patch was made against the 971109 version.

Patrice.