Add more constants for Linux like OS

[LinkTed]

I added more constants for Linux like OS. Most of the new constants are IP_ and IPV6_ related.

[rust-highfive]

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[LinkTed]

I have to check if these constants exist in Linux musl.

[joshtriplett]

@LinkTed CI seems happy with it, which means any constants that this PR adds to musl targets are also available to C on musl in a matching way.

Do you have a specific concern that CI wouldn't have caught here?

[LinkTed]

Oh, I did not know that. Okay if the Linux musl is also tested then it should be fine.