nfnetlink constants

[vorner]

Hello

I'd like to ask, would it be OK to add netfilter netlink constants. They are in the linux headers (/usr/include/linux/netfilter/nfnetlink*.h). I'm trying to extend neli with nfnetlink support (currently NFLOG, jbaublitz/neli#48).

I'll send a pull request, I just wanted to ask first if including these would be OK.

[gnzlbg]

Sure.

[JohnTitor]

I assume this is done by #1628 and am going to close but feel free to re-open if I'm missing something.

[vorner]

I think there are some few more constants in the header, but I guess a lazy approach (once they are actually needed) is good and there's not much use for keeping this issue open :-). Sorry for letting it rot in here.