SUPPORT /CURSOR

        [CLEAN\]SUPPORT /CURSOR

    With option /CURSOR, SUPPORT calls the  interactive  cursor  to  define  the
    polygon  summits.   Type any key to go to next summit, D to correct the last
    one and type E to end the polygon definition. The  last  polygon  side  will
    then  appear. The polygon definition may be aborted by typing Q. For graphi-
    cal displays, you may use the mouse buttons  for  the  commands.   The  left
    mouse  button  draws a vertex, the middle mouse button deletes the last ver-
    tex, and the right mouse button ends the polygon definition.

    The resulting support is available in the Sic structure SUPPORT:
      - SUPPORT%NXY  [Integer]  Number of summits
      - SUPPORT%X    [Double]   X coordinates
      - SUPPORT%Y    [Double]   Y coordinates