INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA, MCGA) - GRAY-SCALE SUMMING

	AH = 12h
	BL = 33h
	AL = new state
	    00h enable gray scale summing
	    01h disable gray scale summing
Return: AL = 12h if function supported
Desc:	specify whether or not colors should be converted to gray scale when
	  palette or color registers are loaded
SeeAlso: AX=101Bh,AX=BF06h,AX=BF08h