termios: Add definition for IUCLC

[3v1n0]

What does this PR do

Adds IUCLC definition

Checklist:

• [x] I have read CONTRIBUTING.md
• [ ] I have written necessary tests and rustdoc comments
• [ ] A change log has been added if this PR modifies nix's API

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Needs: https://github.com/rust-lang/libc/pull/4846 Related: https://github.com/uutils/coreutils/pull/9432

[3v1n0]

Marking a draft until newer libc is released

[3v1n0]

As update, this landed in libc 0.2.178, but... That also broke nix tests, and so we need to wait for the new one that will contain https://github.com/rust-lang/libc/commit/d5b0f290a1c464fecc9710bb7fb1c8e011c1314a 🤯