dhclient needs to have /var/empty and a _dhcp user

(it also needs /sbin/dhclient-script, will handle that later)

release/picobsd/build/mfs.mtree

@@ -58,6 +58,8 @@
     var            
         db             
         ..
+        empty
+        ..
         run            
         ..
         spool          

release/picobsd/floppy.tree/etc/master.passwd

@@ -1,3 +1,4 @@
+# $FreeBSD$
 root:$1$xOOaGnKU$U9QdsCI40XXcCUMBN.7Az.:0:0::0:0:Charlie &:/root:/bin/sh
 toor:*:0:0::0:0:Bourne-again Superuser:/root:
 daemon:*:1:1::0:0:Owner of many system processes:/root:/nonexistent
@@ -5,4 +6,5 @@ operator:*:2:20::0:0:System &:/usr/guest/operator:/bin/csh
 bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/nonexistent
 tty:*:4:65533::0:0:Tty Sandbox:/:/nonexistent
 nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/nonexistent
+_dhcp:*:65:65::0:0:dhcp programs:/var/empty:/usr/sbin/nologin
 user:*:1002:1002:Sample User:0:0:user:/home/user:/bin/sh