INT 14,1 - Send Character to Communications Port

	AH = 01
	AL = character to send
	DX = zero based serial port number (0-1) (0-3 for AT)


	on return:
	AH = port status  (see INT 14,STATUS)
	     bit 7=0 indicates success
	     bit 7=1 indicates error, bits 0-6 indicate cause


	- INT 14,3 should be used to determine the actual cause
	  of the error since the time-out bit of the status register
	  is always set during an error on this call
	- uses hardware flow control