From Bertrand:

 - New classes TGTripleHSlider and TGTripleVSlider :
   Inherit from DoubleSlider widgets and allow easy
   selection of a min, max and pointer value out of
   a range. The pointer position can be constrained
   to edges of slider and / or can be relative to
   the slider position.

 - modification of slider1h.xpm and slider1v.xpm for
   a better design.

 - New tutorial Slider3Demo.C showing the properties
   of these new sliders.


git-svn-id: http://root.cern.ch/svn/root/trunk@13890 27541ba8-7e3a-0410-8455-c3a389f83636