Update bisect script to help find source of python example 15 rendering regression (and other plshade regressions).
Update bisect script to help find source of
python example 15 rendering regression (and other plshade regressions).

svn path=/trunk/; revision=10958

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