Split the crossing event handler into separate enter and leave event handlers to better keep track of whether we should be drawing graphic crosshairs or not.  Now works properly under all combinations of expose, pointer in or out of window, and with or without a pixmap, as far as I can tell.  Added more cool stuff to be done when -debug is specified.
Split the crossing event handler into separate enter and leave event
handlers to better keep track of whether we should be drawing graphic
crosshairs or not.  Now works properly under all combinations of expose,
pointer in or out of window, and with or without a pixmap, as far as I can
tell.  Added more cool stuff to be done when -debug is specified.

svn path=/trunk/; revision=1603

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