extensions: libip[6]t_REDIRECT: use new nft syntax when do xlate

extensions: libip[6]t_REDIRECT: use new nft syntax when do xlate

After commit "parser_bison: redirect to :port for consistency with
nat/masq statement" in nftables tree, we should recommend the end
user to use the new syntax.

Before this patch:
  # iptables-translate -t nat -A PREROUTING -p tcp -j REDIRECT --to-ports 1
  nft add rule ip nat PREROUTING ip protocol tcp counter redirect to 1

Apply this patch:
  # iptables-translate -t nat -A PREROUTING -p tcp -j REDIRECT --to-ports 1
  nft add rule ip nat PREROUTING ip protocol tcp counter redirect to :1

Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>