Update to FreeBSD head 2017-12-01

Git mirror commit e724f51f811a4b2bd29447f8b85ab5c2f9b88266.

Update #3472.

freebsd/bin/hostname/hostname.c

@@ -1,6 +1,8 @@
 #include <machine/rtems-bsd-user-space.h>
 
 /*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
  * Copyright (c) 1988, 1993
  *	The Regents of the University of California.  All rights reserved.
  *