Fixed bug in window cleanup and termination that was causing a core dump for apps using multiple plframe widgets.
Fixed bug in window cleanup and termination that was causing a core dump
for apps using multiple plframe widgets.

svn path=/trunk/; revision=1192

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