Added flag pls->nobg for disabling background color modification.  If set, the device default is used.  You can set pls->nobg by specifying a negative number for the background color.  Useful for including color EPSF files into a document.
Added flag pls->nobg for disabling background color modification.  If set,
the device default is used.  You can set pls->nobg by specifying a
negative number for the background color.  Useful for including color EPSF
files into a document.

svn path=/trunk/; revision=1437

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