Add LINK_STATE_* definitions to NetBSD and OpenBSD.

[pusateri]

Description

Add missing interface LINK_STATE_* definitions from sys/net/if.h

Sources

https://github.com/NetBSD/src/blob/54613ac4db31045d0ca58a7e2da7af005c6b5cd2/sys/net/if.h#L207
https://github.com/openbsd/src/blob/bac4ed8757bbe68d4cac117487958588ae27e7c2/sys/net/if.h#L135

Checklist

• [ x] Relevant tests in libc-test/semver have been updated
• [x ] No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• [ x] Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[rustbot]

Some changes occurred in OpenBSD module

cc @semarie

[semarie]

LGTM. tests are passing on OpenBSD.

[JohnTitor]

Thanks!

[tgross35]

Could you turn the doc comments into regular comments to match the others? Usually we don't add user-facing docs in this crate, instead preferring if the user refers to the manpages.

Also the comments should be permalinks, otherwise they'll wind up getting out of date. On the GH UI you can do this by clicking the triple dots in the top right then "copy permalink".