Add group `network'.

This group is intended for use by network daemons
such as ppp, pppd and slattach.  These programs will
be mode 4550 and group network (soon), allowing the
sys-admin control over who manipulates interface
configurations and routing tables.

src/etc/group

@@ -12,6 +12,7 @@ games:*:13:
 staff:*:20:root
 guest:*:31:root
 utmp:*:45:
+network:*:69:
 ingres:*:74:ingres
 dialer:*:117:
 nogroup:*:32766: