netfilter: ipset: Alignment problem between 64bit kernel 32bit userspace

Sven-Haegar Koch reported the issue:

sims:~# iptables -A OUTPUT -m set --match-set testset src -j ACCEPT
iptables: Invalid argument. Run `dmesg' for more information.

In syslog:
x_tables: ip_tables: set.3 match: invalid size 48 (kernel) != (user) 32

which was introduced by the counter extension in ipset.

The patch fixes the alignment issue with introducing a new set match
revision with the fixed underlying 'struct ip_set_counter_match'
structure.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>