headers/compatibility/bsd: Update headers to remove BSD advertising clause.

Rewrite link.h entirely.

headers/compatibility/bsd/paths.h

@@ -1,4 +1,6 @@
-/*
+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
  * Copyright (c) 1989, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
@@ -10,11 +12,7 @@
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
+ * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
@@ -31,7 +29,6 @@
  * SUCH DAMAGE.
  *
  *	@(#)paths.h	8.1 (Berkeley) 6/2/93
- * $FreeBSD: src/include/paths.h,v 1.25 2004/01/04 17:17:46 iedowse Exp $
  */
 
 #ifndef _PATHS_H_