extensions: libipt_REDIRECT: Add translation to nft

extensions: libipt_REDIRECT: Add translation to nft

Add translation for target REDIRECT to nftables.

Examples:

$ sudo iptables-translate -t nat -A prerouting -p tcp --dport 80 -j REDIRECT --to-ports 8080
nft add rule ip nat prerouting tcp dport 80 counter redirect to 8080

$ sudo iptables-translate -t nat -A prerouting -p tcp --dport 80 -j REDIRECT --to-ports 8080 --random
nft add rule ip nat prerouting tcp dport 80 counter redirect to 8080 random

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