Adding isibootd(8) netboot server for luna68k

[Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>]

Hi,

I'm going to add isibootd(8) command, which is a dumb network boot server
program for the OMRON LUNA clients, like ndbootd(8) for Sun2 machines.

http://www.ceres.dti.ne.jp/tsutsui/netbsd/isibootd/

It's based on isiboot utility written by nisimura@
for early NetBSD/luna68k development:
http://www.NetBSD.org/ports/luna68k/install.html#isiboot
and I've put several updates to integrate it into src/usr.sbin:

 - rename to isibootd and call daemon(3) and pidfile(3)
 - chdir to /tftpboot as a boot file directory by default
 - ignore '/' in requested filename as rbootd(8)
 - check if client's MAC address is in ethers(5) and hosts(5) as ndbootd(8)
 - use getifaddrs(3) rather than SIOCGIFCONF and SIOCGIFFLAGS
 - check and use new cloning _PATH_BPF
 - misc cleanup and cosmetics
 - man page:
---
NAME
     isibootd -- TRFS based network boot server

SYNOPSIS
     isibootd [-d tracelevel] [-i interface] [-s directory]

DESCRIPTION
     The isibootd command is a server which supports OMRON LUNA's network boot
     protocol based on the Transparent Remote File System (TRFS) protocol.
     The TRFS protocol uses special Ethernet type packets and works within a
     local network.

     isibootd is a simple TRFS server that only supports client reads for
     booting and exports files in a specified directory.  isibootd accepts
     requests only from clients listed in the /etc/ethers and have valid host-
     names.

     The options are as follows:

     -d tracelevel
                 Run isibootd in debug mode with specified tracelevel.  The
                 tracelevel can be value 1, 2, or 3, and greater tracelevel
                 provides more detailed trace output.  The server will not
                 fork in the debug mode.

     -i interface
                 Specify a network interface to service network boot.  If not
                 specified isibootd searches available network interfaces
                 (excluding loopback) and use the first configured ``up'' one.

     -s directory
                 Specify a directory containing boot files to be served by
                 isibootd.  If not specified isibootd uses /tftpboot by
                 default.
 :
---

I guess there will be quite few users who want this tool so it
would be almost harmless, but comments are appreciated before import.

Thanks,
---
Izumi Tsutsui