message: range_map: also test size of the internal representation
diff: @@ -203,6 +203,7 @@ mod tests {
  }
  // Check
  assert_eq!(to_vec(&map, 10, 1), vec![42]);
  + assert_eq!(map.map.len(), 3);
  // Insert with size 0
  for x in map.iter_mut(Size::from_bytes(10), Size::from_bytes(0)) {
  @@ -212,6 +213,7 @@ mod tests {
  *x = 19;
  }
  assert_eq!(to_vec(&map, 10, 2), vec![42, -1]);
  + assert_eq!(map.map.len(), 3);
  }
  #[test]
  @@ -223,6 +225,7 @@ mod tests {
  for x in map.iter_mut(Size::from_bytes(15), Size::from_bytes(1)) {
  *x = 43;
  }
  + assert_eq!(map.map.len(), 5);
  assert_eq!(
  to_vec(&map, 10, 10),
  vec![-1, 42, -1, -1, -1, 43, -1, -1, -1, -1]
  @@ -233,6 +236,7 @@ mod tests {
  *x = 23;
  }
  }
  + assert_eq!(map.map.len(), 6);
  assert_eq!(
  to_vec(&map, 10, 10),
  @@ -244,6 +248,7 @@ mod tests {
  for x in map.iter_mut(Size::from_bytes(15), Size::from_bytes(10)) {
  *x = 19;
  }
  + assert_eq!(map.map.len(), 6);
  assert_eq!(map.iter(Size::from_bytes(19), Size::from_bytes(1))
  .map(|&t| t).collect::<Vec<_>>(), vec![19]);
  assert_eq!(map.iter(Size::from_bytes(20), Size::from_bytes(1))
  