* fhandler.cc (fhandler_base::lock): Move to flock.cc.
	(fhandler_base::fixup_after_exec): Reset mandatory_locking.
	* fhandler.h (class fhandler_base): Add mandatory_locking status flag.
	Add mandatory_locking accessor methods.  Accommodate change throughout.
	(fhandler_base::mand_lock): Declare.
	(class fhandler_disk_file): Drop in favor of new status flag.
	* (fhandler_disk_file::fcntl): Call need_fork_fixup if mandatory_locking
	flag gets set.
	* flock.cc (fhandler_base::lock): Define here.
	(flock): Handle mandatory_locking.
	(lockf): Ditto.
	(fhandler_base::mand_lock): Define.