extensions: libxt_owner: Add translation to nft

extensions: libxt_owner: Add translation to nft

Add translation for module owner to nftables.
Full translation of this match awaits the support for --socket-exists
option.

Examples:

$ sudo iptables-translate -t nat -A OUTPUT -p tcp --dport 80 -m owner --uid-owner root -j ACCEPT
nft add rule ip nat OUTPUT tcp dport 80 skuid 0 counter accept

$ sudo iptables-translate -t nat -A OUTPUT -p tcp --dport 80 -m owner --gid-owner 0-10 -j ACCEPT
nft add rule ip nat OUTPUT tcp dport 80 skgid 0-10 counter accept

$ sudo iptables-translate -t nat -A OUTPUT -p tcp --dport 80 -m owner ! --uid-owner shivani -j ACCEPT
nft add rule ip nat OUTPUT tcp dport 80 skuid != 1000 counter accept

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>