NAME
        OpenFromLock -- Opens a file you have a lock on (V36)

   SYNOPSIS
        fh = OpenFromLock(lock)
        D0                 D1

        bptr openfromlock(bptr)

   FUNCTION
        Given a lock, this routine performs an open on that lock.  If the open
        succeeds, the lock is (effectively) relinquished, and should not be
        UnLock()ed or used.  If the open fails, the lock is still usable.
        The lock associated with the file internally is of the same access
        mode as the lock you gave up - shared is similar to MODE_OLDFILE,
        exclusive is similar to MODE_NEWFILE.

   INPUTS
        lock - lock on object to be opened.

   RESULT
        fh   - Newly opened file handle or NULL for failure

   BUGS
        In the original V36 autodocs, this was shown (incorrectly) as
        taking a Mode parameter as well.  The prototypes and pragmas were
        also wrong.

   SEE ALSO
        open(), close(), lock(), unlock()