pixman: Changes to 'blend-mode'

[Benjamin Otte]

New branch 'blend-mode' available with the following commits:
commit 9ee1b2165c622575ef9a18b9686b5cee2762720e
Author: Benjamin Otte <otte at gnome.org>
Date:   Thu Sep 25 12:53:06 2008 +0200

    Add support for extended blend mode. First pass.
    
    This adds support only for FbCombineU function.
    This work is based on equations provided in SVG 1.2 specification draft.
    
    http://www.w3.org/TR/SVG12/
    
    Based on a previous patch by Emmanuel Pacaud <emmanuel.pacaud at free.fr>