INT 15 - Intel System Management Bus - RETRIEVE CRITICAL MESSAGES

	AX = 53B0h
	BH = 07h
	CX = 6941h ('iA')
Return: CF clear if successful
	    AH = 00h (SMBus OK)
	    AL = device address
	    BX = device message
	CF set if error
	    AH = error code (05h,07h,08h,09h,0Ah,86h) (see #00484)
Desc:	retrieves oldest queued critical message from an SMBus device to the
	  host
Notes:	up to five messages are queued; if the queue is full, messages will be
	  lost and error 09h returned