Changed the -bg flag to accept a full-color argument in the form -bg rrggbb, with rr, gg, bb corresponding to the background RGB values in hex.  Example: -bg FFFF00 to get a yellow background.
Changed the -bg flag to accept a full-color argument in the form
-bg rrggbb, with rr, gg, bb corresponding to the background RGB
values in hex.  Example: -bg FFFF00 to get a yellow background.

svn path=/trunk/; revision=164

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