packages: ipv6/tayga: move static mappings to 'firewall' config

packages: ipv6/tayga: move static mappings to 'firewall' config

Static NAT64 entries should really belong to firewall config and could
be also processed by firewall code.

Currently tayga only processes ipv4_addr and ipv6_addr options, this is
the mapping itself.  ipv4_addr is taken from dynamic pool and is not
accessable from anywhere.  In addition, firewall code may add DNAT/SNAT
rules to map it to address from WAN interface and permit access from WAN
zone using selected ports/protocols.  Furthermore, firewall may allow or
deny access to ipv6_addr from 4-to-6 translated addresses.

Example:

config nat64
	option ipv4_addr 192.0.2.31
	option ipv6_addr 2001:db8::31

Signed-off-by: Alexey I. Froloff <raorn@altlinux.org>
git-svn-id: svn://svn.openwrt.org/openwrt/packages@30582 3c298f89-4303-0410-b956-a3cf2f4a3e73