INT 62 u - FGDRIVER v1.10 - "FG_SCROLL" - VERTICALLY SCROLL SCREEN REGION
        AX = 0067h
        BX = left edge column
        CX = right edge column
        DX = top edge row
        SI = bottom edge row
        DI = number of pixels by which to scroll (positive scrolls up,
                negative scrolls down)
        ES = type of scroll
            0000h circular (rows scrolled off are copied to vacated rows)
            else vacated rows are filled with the current color
Notes:  in graphics modes, the left and right edges are adjusted to byte
          boundaries if necessary
        circular scrolling uses part of the hidden page as a workspace