Add code to xwin driver to detect and handle WM_DELETE_WINDOW client messages (i.e. pressing the window close button), consistent with the qtwidget driver.
Add code to xwin driver to detect and handle WM_DELETE_WINDOW client messages (i.e. pressing the window close button), consistent with the qtwidget driver.


svn path=/trunk/; revision=10980

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