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

                                                     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.

See Also: INT 67H: EMM Services
          Extended Memory Specification (XMS)
          Interrupts and BIOS Services
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