Correct typo: require Octave >= 2.1.50 and not 2.1.51
Correct typo: require Octave >= 2.1.50 and not 2.1.51

svn path=/trunk/; revision=5103

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