NAME
	DupLockFromFH -- Gets a lock on an open file (V36)

   SYNOPSIS
	lock = DupLockFromFH(fh)
	D0                   D1

	BPTR DupLockFromFH(BPTR)

   FUNCTION
	Obtain a lock on the object associated with fh.  Only works if the
	file was opened using a non-exclusive mode.  Other restrictions may be
	placed on success by the filesystem.

   INPUTS
	fh   - Opened file for which to obtain the lock

   RESULT
	lock - Obtained lock or NULL for failure

   SEE ALSO
	DupLock(), Lock(), UnLock()