NAME
	CMD_CLEAR -- Clear the keyboard input buffer.

   FUNCTION
	Remove from the input buffer any keys transitions waiting to
	satisfy read requests.

   IO REQUEST
	io_Message	mn_ReplyPort set if quick I/O is not possible
	io_Device	preset by the call to OpenDevice
	io_Command	CMD_CLEAR
	io_Flags	IOB_QUICK set if quick I/O is possible