RUSTSEC-2020-0122 beef::Cow lacks a Sync bound on its Send trait allowing for data races

Affected versions of this crate did not have a T: Sync bound in the Send impl for Cow. This allows users to create data races by making Cow contain types that are Send && !Sync like Cell or RefCell. Such data races can lead to memory corruption. The flaw was corrected in commit d1c7658 by adding...