HTTP response version

Hi! I'm writing a little bit of [`http` interop code](https://crates.io/crates/http) in [a crate](https://github.com/ramosbugs/oauth2-rs/issues/236), and running into the need of the _HTTP response version_. I seem to only be able to _set_ a preferred HTTP version with this `Easy` portion of the crate.

I'm not super familiar with `curl`, but it seems [the bindings](https://curl.se/libcurl/c/curl_easy_getinfo.html) have `CURLINFO_HTTP_VERSION` for this, but I have no clue how new it is nor does it appear to be in the bindings already. Are the `curl-sys` bindings autogenerated or written by hand?

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Note that we could separately discuss whether this `curl` crate should have built-in (behind an optional crate feature) `http` interop support, now that they've had their `1.0.0` release?