Put in missing type cast required by Visual C++ (as reported by Olof Svensson).
Put in missing type cast required by Visual C++ (as reported by Olof
Svensson).

svn path=/trunk/; revision=3382

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