Rust 1.63.0 released

Version1.63.0 of the Rust language has been released. Changes include theaddition of scoped threads, a new ownership model for raw file descriptors,and the completion of the borrow-checker transition:

As detailed in thisblog post, we've fully removed the previous lexical borrowchecker from rustc across all editions, fully enabling thenon-lexical, new, version of the borrow checker. Since the borrowchecker doesn't affect the output of rustc, this won't change thebehavior of any programs, but it completes a long-running migration(started in the initial stabilization of NLL for the 2018 edition)to deliver the full benefits of the new borrow checker across alleditions of Rust. For most users, this change will bring slightlybetter diagnostics for some borrow checking errors, but will nototherwise impact which code they can write.