message: h3: misc cleanups
  Replace &String with &str in fn params, this is almost always preferable.
  Use into() instead of String::from(), less words.
  rustfmt also did some whitespace changes.
diff: @@ -44,24 +44,24 @@ struct Request {
  impl Request {
  pub fn new(
  - method: &String,
  - scheme: &String,
  - host: &String,
  - path: &String,
  + method: &str,
  + scheme: &str,
  + host: &str,
  + path: &str,
  headers: &Vec<(String, String)>,
  ) -> Request {
  let mut r = Request {
  - method: method.clone(),
  - scheme: scheme.clone(),
  - host: host.clone(),
  - path: path.clone(),
  + method: method.to_owned(),
  + scheme: scheme.to_owned(),
  + host: host.to_owned(),
  + path: path.to_owned(),
  headers: Vec::new(),
  buf: None,
  };
  - r.headers.push((String::from(":method"), method.clone()));
  - r.headers.push((String::from(":scheme"), r.scheme.clone()));
  - r.headers.push((String::from(":authority"), r.host.clone()));
  - r.headers.push((String::from(":path"), r.path.clone()));
  + r.headers.push((":method".into(), method.to_owned()));
  + r.headers.push((":scheme".into(), r.scheme.clone()));
  + r.headers.push((":authority".into(), r.host.clone()));
  + r.headers.push((":path".into(), r.path.clone()));
  r.headers.extend_from_slice(&headers);
  r
  }
  @@ -149,10 +149,10 @@ impl ClientRequest {
  pub fn new(
  role: Role,
  stream_id: u64,
  - method: &String,
  - scheme: &String,
  - host: &String,
  - path: &String,
  + method: &str,
  + scheme: &str,
  + host: &str,
  + path: &str,
  headers: &Vec<(String, String)>,
  ) -> ClientRequest {
  qdebug!("Create a request stream_id={}", stream_id);
  @@ -682,10 +682,10 @@ impl HttpConn {
  pub fn fetch(
  &mut self,
  - method: &String,
  - scheme: &String,
  - host: &String,
  - path: &String,
  + method: &str,
  + scheme: &str,
  + host: &str,
  + path: &str,
  headers: &Vec<(String, String)>,
  ) -> Res<()> {
  let id = self.conn.stream_create(StreamType::BiDi)?;
  