Polished last addition by Alan Irwin.  Added Docbook markup in appropriate places.  Also, changed several <literal> tags to <envar>, which is the appropriate tag for environment variables.
Polished last addition by Alan Irwin.  Added Docbook markup in appropriate
places.  Also, changed several <literal> tags to <envar>, which is the
appropriate tag for environment variables.

svn path=/trunk/; revision=5559

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