Tweak: use copy method to keep xg0t completely independent of xg0.
Tweak: use copy method to keep xg0t completely independent of xg0.

svn path=/trunk/; revision=3702

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