Fix /etc/network usage (Pablo Neira)

Fix /etc/network usage (Pablo Neira)

http://bugs.debian.org/398082

iptables 1.3.5 and 1.3.6 appear to read /etc/networks, but the
information is lost somewhere with 1.3.6.

 # cat /etc/networks
 foonet 10.0.0.0

 # strace -s 255 -o /tmp/foo iptables -v -A INPUT -s foonet/8 -j
ACCEPT #1.3.5 [1]
 ACCEPT  all opt -- in * out *  10.0.0.0/8  -> 0.0.0.0/0

 # strace -s 255 -o /tmp/bar iptables -v -A INPUT -s foonet/8 -j
ACCEPT #1.3.6 [2]
 iptables v1.3.6: host/network `foonet.0.0.0' not found
 Try `iptables -h' or 'iptables --help' for more information.

1. http://people.debian.org/~ljlane/stuff/strace-iptables-1.3.5.txt
2. http://people.debian.org/~ljlane/stuff/strace-iptables-1.3.6.txt