Compatibility: EMS 3.2+
Expects: AX    4c00H
                                                                  
Returns: AH    EMM status (0=successful)
                                                                  
Info: This obtains the number of active EMM handles.  You might use
this to calculate the buffer size needed for INT 67H 4d00H.

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INT 67H 4c00H: Count Active Handles