INT 2F - AVATAR(Advanced Video Attribute Terminal Assembler and Recreator) A set of control codes which may be used to affect the output of characters to the screen on systems equipped with an appropriate driver.	 Similar in intent to ANSI sequences, AVATAR has shorter command sequences and provides additional PC-specific functionality. AVATAR is primarily used by the Opus and Maximus bulletin board systems (it was designed by one of the developers of the Opus system). Serial Dispatcher - INSTALL IRQ4 HANDLER
	AX = 1A43h
	BX = 4156h ('AV')
	ES:DI -> FAR handler for serial port using IRQ4
	DS = data segment needed by handler
Return: AX = status/return value
	    0000h if no more room
	    1A43h if ASD not installed
	    else handle to use when uninstalling
Notes:	(see AX=1A42h)
SeeAlso: AX=1A42h,AX=1A63h