Clean up the script so that any unexpected error terminates the
script, and stop suppressing errors that may contain useful
information (for example, that you are using the stable version but
need to use the nightly).
This is useful because if hyper.h is not up to date going forward the
CI should flag it. As is, there are a bunch of changes to hyper.h that
have not been checked in (or were generated by a newer version of the
cbindgen script.)
Fixes#2483.
This adds an internal ability to copy the HTTP/1 reason-phrase and place
it in the `http::Extensions` of a response, if it doesn't match the
canonical reason. This could be exposed in the Rust API later, but for
now it is only used by the C API.
