[http] Double free in http

An issue was discovered in the http crate before 0.1.20 for Rust. The HeaderMap::Drain API can use a raw pointer, defeating soundness.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-25009
• https://rustsec.org/advisories/RUSTSEC-2019-0034.html
• https://github.com/advisories/GHSA-6rhx-hqxm-8p36