message: handle MaxData frames
  reorg use statements.
diff: #![allow(unused_variables)]
  +use std::cmp::max;
  +use std::collections::{HashMap, HashSet};
  +use std::fmt::{self, Debug};
  +use std::net::SocketAddr;
  +use std::ops;
  +
  +use rand::prelude::*;
  +
  use crate::data::Data;
  use crate::frame::{decode_frame, Frame};
  use crate::nss::*;
  use crate::packet::*;
  -use crate::{Error, Res};
  -
  use crate::stream::{BidiStream, Recvable, RxStreamOrderer, TxBuffer};
  -use rand::prelude::*;
  -use std::collections::{HashMap, HashSet};
  -use std::fmt::{self, Debug};
  -use std::net::SocketAddr;
  -use std::ops;
  +use crate::{Error, Res};
  #[derive(Debug, Default)]
  struct Packet(Vec<u8>);
  @@ -401,7 +403,7 @@ impl Connection {
  } => {
  self.process_inbound_stream_frame(fin, stream_id, offset, data)?;
  }
  - Frame::MaxData { maximum_data } => {} // TODO(agrover@mozilla.com): set self.max_data?
  + Frame::MaxData { maximum_data } => self.max_data = max(self.max_data, maximum_data),
  Frame::MaxStreamData {
  stream_id,
  maximum_stream_data,
  