[xcb] Unchecked Return Value in xcb

An issue was discovered in the xcb crate through 2021-02-04 for Rust. It has a soundness violation because xcb::xproto::GetAtomNameReply::name() calls std::str::from_utf8_unchecked() on unvalidated bytes from an X server.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-26955
• https://github.com/RustSec/advisory-db/issues/653
• https://rustsec.org/advisories/RUSTSEC-2021-0019.html
• https://github.com/advisories/GHSA-3288-cwgw-ch86