Expects: AX    001fH
                                                                  
Returns: AX    status: 001fH=deactivated OK
ffffH=can't deactivate
ES:DX address of previous INT 33H handler
                                                                  
Info: This deactivates the mouse driver.  All interrupts used by the
mouse support are disabled, effectively eliminating all mouse
support.

Use INT 33H 0021H to re-enable all interrupts used by the mouse
support.

Note that the INT 33H vector remains in place, but the only
function it can perform is INT 33H 0021H (to re-enable).

You might call this just before replacing the mouse support with
your own system of interrupts and kludges.  Then use the return
value in ES:DX to reinstall the previous INT 33H code at some
later time (i.e., when you exit to DOS).

- -

INT 33H 001fH: Deactivate Mouse Driver