Add iked support for route based sec(4) tunnels.

Add iked support for route based sec(4) tunnels.

To use sec(4) instead of policy based tunnels, create a sec(4)
interface and add 'iface secXX' to your policy config.
sec(4) interfaces also support auto configuration for dynamic client
IPs via 'request any' like all other interfaces.
The config won't work without traffic selectors, 'from any to any'
should work for now but I plan to make this optional in the future.

ok dlg@