message: Better packet dump visuals
diff: @@ -612,7 +612,7 @@ impl Connection {
  continue;
  }
  };
  - dump_packet(self, "rx", &hdr, &body);
  + dump_packet(self, "<- RX", &hdr, &body);
  // TODO(ekr@rtfm.com): Have the server blow away the initial
  // crypto state if this fails? Otherwise, we will get a panic
  @@ -868,7 +868,7 @@ impl Connection {
  .unwrap();
  let tx = cs.tx.as_ref().unwrap();
  let mut packet = encode_packet(tx, &hdr, &encoder);
  - dump_packet(self, "tx", &hdr, &encoder);
  + dump_packet(self, "TX ->", &hdr, &encoder);
  out_bytes.append(&mut packet);
  }
  