FreeBSDLike: Remove obsolete constants in version 1.0.0

[kellda]

Fixes #454

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[JohnTitor]

So, this is 1.0-breakage and I'll hold off until we're ready to prepare 0.3 or 1.0 like #1794.

[JohnTitor]

This constant isn't deprecated.

[asomers]

But it should be. And in fact, it has been removed in FreeBSD 13. How about we remove it in this PR, and I submit another that deprecates it immediately (a non breaking change)?

[JohnTitor]

Generally I'd like to avoid a breaking change unless it breaks the build. So, the problem here is that we don't have any policies for supported FreeBSD versions like #1412 IIRC. We have hidden the items and added deprecation notes, I feel it's enough here, isn't it? One possible way is to tweak the deprecation notes like "We plan to remove this in 0.2.7x" so that users notice the removal.
Deprecating CTL_P1003_1B_MAXID is welcome, of course.

[asomers]

In this case, relying on those constants could cause misbehavior at runtime, which IMHO is worse than a broken build, because it's harder to detect. There is precedent for removing similar constants which vary from OS release to OS release: 215f095

[JohnTitor]

In 215f095, we told the user to leave a comment in the deprecation notes as I suggested above. But we don't do it yet for CTL_MAXID and others.

[asomers]

You should also remove these constants from libc-test/build.rs .

[bors]

☔ The latest upstream changes (presumably #1844) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #2898) made this pull request unmergeable. Please resolve the merge conflicts.

[tgross35]

@kellda main is now intended for 1.0. The changes look good to me, are you able to rebase this?

@rustbot author

[tgross35]

Thanks! Could you squash the commits? LGTM after that

[tgross35]

I should be able to merge this after CI gets fixed.

@asomers could you ack the change?