INT 7F - Alloy NTNX - UNLOCK FILE FOR USER
        AH = 42h
        AL = user ID
        DS:DX -> ASCIZ filename
Return: AL = status
            00h successful
            01h invalid function
            02h already locked
            03h unable to lock
            04h lock table full
SeeAlso: AH=00h,AH=41h"NTNX",AH=42h"MW386"

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