In some scenarios (e.g. 464xlat) it is desirable to not route the mapped
prefix to tayga's interface. This adds an option 'noroutes' which, when
set to 1, will prevent such routes from being added.

Signed-off-by: Nils Schneider <nils@nilsschneider.net>

This patch integrates tayga with netifd. Parametres are nearly same as
with the older scripts. Support for static mapping of IPv4<=>IPv6 addresses
is missing. Example configuration:

config interface 'nat64'
        option proto 'tayga'
        option prefix 64:ff9b::/96
        option dynamic_pool 10.128.0.0/24
        option ipv4_addr 10.128.0.1	#address of the TAYGA itself
        option ipv6_addr 2001:470:5990::64
        option ipaddr  192.168.1.1 #optional address of TUN interface
        option ip6addr 2001:db8::1

Signed-off-by: Ondrej Caletka <ondrej@caletka.cz>