INT 21 - DOS 1+ - WRITE CHARACTER TO STDAUX                                     
	AH = 04h
	DL = character to write
Notes:	keyboard checked for ^C/^Break, and INT 23 executed if detected
	STDAUX is usually the first serial port
	if STDAUX is busy, this function will wait until it becomes free
SeeAlso: AH=03h,INT 14/AH=01h,INT E0/CL=04h