INT 62 u - FGDRIVER v4.02 - "FG_YALPHA" - CONVERT SCREEN ROW TO CHARACTER ROW
	AX = 00E4h
	BX = screen space row
Return: AX = character space row containing specified coordinate
Note:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474 at AX=0000h)
SeeAlso: AX=00E1h,AX=00E5h