Added check to make sure ASCII point drawing routines don't try to use a font that has been unloaded.
Added check to make sure ASCII point drawing routines don't try to use
a font that has been unloaded.

svn path=/trunk/; revision=1917

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