netfilter: ipset: Support comments in the list-type ipset.

This provides kernel support for creating list ipsets with the comment
annotation extension.

Signed-off-by: Oliver Smith <oliver@8.c.9.b.0.7.4.0.1.0.0.2.ip6.arpa>
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>