Compatibility: EMS 3.2+
Expects: AX    4500H
DX    EMM Handle (as obtained via INT 67H 4300H)
                                                                  
Returns: AH    EMM status (0=successful)
                                                                  
Info: Release memory allocated via INT 67H 4300H and makes the DX
handle invalid for future calls.

- -

INT 67H 4500H: Close EMM Handle and Free Memory