INT 2F - Communicating Applications Specification - GET/SET AUTORECEIVE
        AX = CB0Fh
        DL = subfunction
            00h get current autoreceive state
            01h set autoreceive state
                DH = number of rings before answer, 00h = never
Return: AX = 0000h autoreceive disabled
           = N     number of rings before answer
           < 0     error code (see AX=CB01h)