XYGraph__PlotSymbol (ul_pbar_graphics)

 *  Synopsis:
 *    #include <ul_pbar_graphics:xygraph.h>
 *
 *    TXYGraph__Result XYGraph__PlotSymbol( TXYGraph__Data xData,
 *					    TXYGraph__Data yData,
 *					    int color, int symbol, int size )
 *
 *  Function intent:
 *    XYGraph__PlotSymbol() plots a specified symbol at a single data point
 *    with a specified display color.
 *  Function parameters:
 *    TXYGraph__Data	xData		X coordinate
 *    TXYGraph__Data	yData		Y coordinate
 *    int		color		Symbol color
 *    int		symbol		Symbol name:
 *					  WN_CIRCLE -> circle,
 *					  WN_SQUARE -> square,
 *					  WN_TRIANGLE -> triangle,
 *					  WN_CROSS -> cross (plus),
 *					  WN_DIAMOND -> diamond
 *    int		size		Symbol size in pixels
 *  Function return value:
 *    CBS_OK		success
 *    CBS_NOSETUP	XYGraph__DisplayGraph() not yet called
 *    else 		wn_xxx() function error occured