NAME
       CloseDevice -- close the serial port

   SYNOPSIS
       CloseDevice(deviceNode)
                    A1
   FUNCTION
       This is an exec call that terminates communication with the
       serial device.  Upon closing, the device's input buffer is freed.

       Note that all IORequests MUST be complete before closing.
        If any are pending, your program must abortio() then waitio()
       to complete them.

   INPUTS
       deviceNode - pointer to the device node, set by open

   SEE ALSO
       serial.device/opendevice()