NAME
        DupLock -- Duplicate a lock

    SYNOPSIS
        lock = DupLock( lock )
        D0              D1

        bptr duplock(bptr)

    FUNCTION
        DupLock() is passed a shared filing system lock.  This is the ONLY
        way to obtain a duplicate of a lock... simply copying is not
        allowed.

        Another lock to the same object is then returned.  It is not
        possible to create a copy of a exclusive lock.

        A zero return indicates failure.

    INPUTS
        lock - BCPL pointer to a lock

    RESULTS
        newLock - BCPL pointer to a lock

    SEE ALSO
        lock(), unlock(), duplockfromfh(), parentoffh()