netconfig.h: sync with upstream.

Bring some comments and the license.
Add SPDX License ID tag while here.

Obtained from:	NetBSD (CVS rev 1.2, 1.5, 1.6)

include/netconfig.h

@@ -1,6 +1,36 @@
-/*	$NetBSD: netconfig.h,v 1.1 2000/06/02 22:57:54 fvdl Exp $	*/
+/*	$NetBSD: netconfig.h,v 1.6 2008/04/28 20:22:54 martin Exp $	*/
 /*	$FreeBSD$ */
 
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-NetBSD
+ *
+ * Copyright (c) 2004 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Frank van der Linden.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
 
 #ifndef _NETCONFIG_H_
 #define _NETCONFIG_H_
@@ -30,10 +60,10 @@ typedef struct {
 /*
  * nc_semantics values
  */
-#define NC_TPI_CLTS	1
+#define NC_TPI_CLTS	1	/* Connectionless transport */
-#define NC_TPI_COTS	2
+#define NC_TPI_COTS	2	/* Connection oriented transport */
-#define NC_TPI_COTS_ORD	3
+#define NC_TPI_COTS_ORD	3	/* Connection oriented, ordered transport */
-#define NC_TPI_RAW	4
+#define NC_TPI_RAW	4	/* Raw connection */
 
 /*
  * nc_flag values