Add rcorder-visualize.sh, which generates graphviz from rc.d scripts

This is imported from NetBSD.  The author--Joerg Sonnenberger--agreed
to apply a two-clause BSD license, just so the license was clear.

This source tree location matches NetBSD, and is the first place someone
might look for such a tool.

Obtained from:	Joerg Sonnenberger via NetBSD
MFC after:	3 days
Sponsored by:	Dell EMC

sbin/rcorder/rcorder-visualize.sh

@@ -0,0 +1,52 @@
+#!/bin/sh
+# $NetBSD: rcorder-visualize.sh,v 1.5 2009/08/09 17:08:53 apb Exp $
+#
+# Copyright (c) 2009 by Joerg Sonnenberger
+# All rights reserved.
+#
+# 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 AUTHOR ``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 AUTHOR 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.
+#
+# $FreeBSD$
+#
+# Simple script to show the dependency graph for rc scripts.
+# Output is in the dot(1) language and can be rendered using
+#	sh rcorder-visualize | dot -T svg -o rcorder.svg
+# dot(1) can be found in graphics/graphviz in pkgsrc.
+
+rc_files=${*:-/etc/rc.d/*}
+
+{
+echo ' digraph {'
+for f in $rc_files; do
+< $f awk '
+/# PROVIDE: /	{ provide = $3 }
+/# REQUIRE: /	{ for (i = 3; i <= NF; i++) requires[$i] = $i }
+/# BEFORE: /	{ for (i = 3; i <= NF; i++) befores[$i] = $i }
+
+END {
+	print "    \"" provide "\";"
+	for (x in requires) print "    \"" provide "\"->\"" x "\";"
+	for (x in befores) print "    \"" x "\"->\"" provide "\";"
+}
+'
+done
+echo '}'
+}