Add netlink protocol values to socket consts

[mrjana]

Signed-off-by: Jana Radhakrishnan mrjana@gmail.com

[fiveop]

Our goal is to have constant definitions in rust-lang/libc use them in nix. The reason is that libc has code that tests whether the values are correct and to avoid code duplication between the two projects. (See CONVENTIONS.md).

Since libc also links against linux/netlink.h you should be able to add these constants in libc. Once in there, you can adapt this PR to reference the libc constants.

Thank you.

[mrjana]

@fiveop Thanks for the pointer. Will fix it in rust-lang/libc.

[fiveop]

@mrjana, are you planning on adapting this PR, now that rust-lang/libc#400 has been merged?

[mrjana]

@fiveop Yes, will do so this week.

[posborne]

@mrjana Any progress on this one?

[Susurrus]

@mrjana Are you still interested in getting this merged?

[mrjana]

@Susurrus Oh shoot! Thanks for the ping. Forgotten about it as I got busy with work. Will get it in soon.

[Susurrus]

These constants are already defined in libc and #647 is going to do away with the consts module completely, so this change is no longer necessary. I'm going to close this.