Inserted workaround for cases where NULL was being used as argument to strcmp (some systems don't like it).
Inserted workaround for cases where NULL was being used as argument to
strcmp (some systems don't like it).

svn path=/trunk/; revision=1332

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