boost::property_tree::write_json(stream, root, /*pretty=*/false) gives extra std::endl at the end

[anonymous]

As was noted in #3828, not pretty written json has extra endl at the end.

(Creating a separate ticket, as that one was Fixed and further comments got ignored)

[Erich Keane <erich.keane@…>]

I submitted a pull request for what I believe is a solid fix for this that does the least harm here: ​https://github.com/boostorg/property_tree/pull/23.

I wonder if the flush behavior is a necessity, but I included it figuring we can remove it easily enough.