INT 33 - MS MOUSE - DEFINE TEXT CURSOR
        AX = 000Ah
        BX = hardware/software text cursor
            0000h software
                CX = screen mask
                DX = cursor mask
            0001h hardware
                CX = start scan line
                DX = end scan line
Note:   when the software cursor is selected, the char/attribute data at the
          current screen position is ANDed with the screen mask and then XORed
          with the cursor mask
SeeAlso: INT 62/AX=007Eh