INT 2F - Intel Image Processing Interface - SELECT SCAN LINE
        AX = CD03h
        BX = scan line
        CX = requested density in dots per inch (300, 600, or 1200)
Return: AL = 00h succesful
                CX = density at which scan line was mapped
                ES:DI -> start of scan line
        AL = 80h unsuccessful
           = 81h scan line out of range
           = 82h unsupported scan line density
           = 83h out of memory