SetGraphMode procedure

  DECLARATION:  SetGraphMode(Mode : Integer);

      PURPOSE:  Set the systems to a graphics mode

         UNIT:  Graph

      REMARKS:  Mode must be a valid mode for the current device driver.
                Use SetGraphMode to to select a graphics mode other than
                the default mode which will be set by InitGraph.

                SetGraphMode restores all graphics settings to their default
                values.  This includes color, palette, current pointer,
                viewport, etc.

                If an attempt is made to select an invalid mode for the
                current device driver, GraphResult will return a value of
                -10 (grInvalidMode)

                NOTE: Errors are returned through GraphResult.

 RESTRICTIONS:  InitGraph must be successfully called first