message: Simplify comment scanner
diff: @@ -49,14 +49,10 @@ impl<R: Read> PPMDecoder<R> {
  Err(err) => return Some((*partof, Err(err))),
  Ok(byte) => byte,
  };
  - if *partof && byte == b'#' {
  - *partof = false;
  - return Some((false, Ok(byte)));
  - } else if !*partof && (byte == b'\r' || byte == b'\n') {
  - *partof = true;
  - return Some((false, Ok(byte)));
  - }
  - return Some((*partof, Ok(byte)));
  + let cur_enabled = *partof && byte != b'#';
  + let next_enabled = cur_enabled || (byte == b'\r' || byte == b'\n');
  + *partof = next_enabled;
  + return Some((cur_enabled, Ok(byte)));
  });
  for (_, byte) in mark_comments.filter(|ref e| e.0) {
  