message: Ord for FrozenStringValue
  Summary: Needed in the following diff, but good to have anyway.
diff: @@ -193,6 +193,18 @@ impl<'v> Ord for StringValue<'v> {
  }
  }
  +impl PartialOrd for FrozenStringValue {
  + fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
  + self.as_str().partial_cmp(other.as_str())
  + }
  +}
  +
  +impl Ord for FrozenStringValue {
  + fn cmp(&self, other: &Self) -> Ordering {
  + self.as_str().cmp(other.as_str())
  + }
  +}
  +
  impl<'v> StringValue<'v> {
  /// Construct without a check that the value contains a string.
  ///
  