INT 33 - MS MOUSE - RETURN POSITION AND BUTTON STATUS
        AX = 0003h
Return: BX = button status
           bit 0  left button pressed if 1
           bit 1  right button pressed if 1
           bit 2  middle button pressed if 1 (Mouse Systems/Logitech mouse)
        CX = column
        DX = row
SeeAlso: AX=000Bh,INT 2F/AX=D000h"ZWmous"