Forked external Rust crates

This directory contains crates which are vendored in order to be modified locally. Each crate must have a README.fuchsia markdown file in its root which answers these questions:

• What is this crate used for?
• Are there any use restrictions? i.e. only for development hosts
• What differs from upstream? Include a changelog if feasible.
• Are there any restrictions to how it should be rolled?
• Is there anything else which makes this dependency “special”?