libc: remove TIOCMGDTRWAIT and TIOCMSDTRWAIT for freebsd15

[mbyx]

Description

FreeBSD 15 removed TIOCMGDTRWAIT and TIOCMSDTRWAIT, so the corresponding constants are changed to only appear in FreeBSD 13 and 14 builds.

Sources

freebsd/freebsd-src@4b4cf0d
https://cgit.freebsd.org/src/commit/?id=4b4cf0d52c43e33c32983df60a8ea16b3d9e2f20

Checklist

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

[mbyx]

This fixes the error in freebsd15 related to these constants, so that we now get the same issue as #4651. Since fixing it is being actively worked on in rust-lang/rust#134697, eventually freebsd15 will fix itself.

[tgross35]

LGTM, cc @asomers for FreeBSD

[asomers]

Those ioctls have been unused since FreeBSD 8. So you should remove them entirely, rather than just for freebsd 15 builds. Since this PR targets the main branch, backwards-compatibility concerns are relaxed.

When applying this change to the libc-0.2 branch, we should mark the symbols as deprecated, rather than removing them.

[asomers]

Also, you should avoid removing the symbols from DragonflyBSD builds, if that was not your intention.

[tgross35]

For future reference, it's a bit easier to just deprecate things on main rather than remove them directly. This just lets me cherry pick the commit as-is rather than recreating as a deprecation.

It will be easy to find+delete everything that's deprecated just before the 1.0 release, whenever that is.