revamped ipv6 patch.

inet6 ip can go directly in ip field, and both ipv4 and 6 can use cidr
notation instead of netmask. all checks are updated to account for these
new rules.

Statechange has been reverted to a must less invasive form, and
net-physical now handles dhcp6 and auto6 properly.

the ip6 field doesn't work anymore. It is recommended if you were
using my old ip6 patch, update the xml files under /etc/zones
to change the ip6 field to ip, and remove the mask bits from
the cidr notation in that field (or destroy and recreate
the zones)