Option to enable dnsmasq default gateway without adding 0.0.0.0/1 and 128.0.0.0/1 routes

[alexeypetrenko]

trafficstars

Currently, it is possible to enable default gateway in dnsmasq and add two routes by using ROUTE_SPOOF option, or to disable default gateway completely. I feel that there should be an option to define a default gateway and not to push out any other routes. That's what this pull request is about.

I moved this part of a functionality out of ROUTE_SPOOF to a DEFAULT_GATEWAY option.

At the same time it remains backward compatible. If anyone enables ROUTE_SPOOF it also pushes default gateway.

Also, I attached a payload net_over_wifi.txt. It doesn't do anything besides forwarding all the trafic through P4wnP1 and WiFi. It's not hard to add some meaningful network MitM attacks on top of it.