2008-03-31 Nnamdi Onyeyiri <http://nnamdi.co.uk>

    * painter.php (Gradient): Added a new class "Gradient" to encapsulate 
    gradient patterns for the gradient fill functions.

    * painter.php (Painter->GradFillRect): Modified to use new Gradient class.
    
    * painter.php (Painter->GradFillEllipse): Added Ellipse gradient filling.
    
    * painter.php (Painter->GradFillArc): Added Arc gradient filling.  This is 
    slightly buggy still and provides the incorrect result unless the gradient 
    is horizontal and the arc starts at angle 0.