extensions: libxt_MASQUERADE: rename IPv4 manpage and tell about IPv6 support

also update list of protocols valid for port mapping.

Signed-off-by: Mart Frauenlob <mart.frauenlob@chello.at>
Signed-off-by: Florian Westphal <fw@strlen.de>
extensions: libxt_LOG: rename IPv4 manpage and tell about IPv6 support

Signed-off-by: Mart Frauenlob <mart.frauenlob@chello.at>
Signed-off-by: Florian Westphal <fw@strlen.de>