Classify FIXMEs in repo - 2

[lvllvl]

Description

Responding to #4117, added labels to all FIXMEs in repo. Breaking this up into multiple PRs for review.

Sources

Checklist

• Relevant tests in libc-test/semver have been updated
  • Not applicable
• 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
  • Not applicable

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @tgross35 (or someone else) some time within the next two weeks.

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[rustbot]

Some changes occurred in the Android module

cc @maurer

[tgross35]

Left a couple comments, please also the debug changes from #4229 (review). You can probably just find+replace those