Drop the boundary stroke for partially opaque filled regions in the cairo driver similar to the change in the svg driver (Revision 9232).
Drop the boundary stroke for partially opaque filled regions in the cairo driver similar to the change in the svg driver (Revision 9232).

svn path=/trunk/; revision=9297

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot