Stenberg: Dropping hyper

Curl maintainer Daniel Stenberg announces
that the curl project will be dropping hyper, its experimental HTTP backend
written in Rust, due to lack of developer interest.

While the experiment itself is deemed a failure, I think we learned
from it and improved curl in the process. We had to rethink and
reassess several implementation details when we aligned HTTP
behavior with hyper. libcurl parses and handles HTTP stricter
now. Better.