This is a bugfix release. ## Broker - Fix build failure when using `WITH_ADNS=yes` - Ensure that an error occurs if `per_listener_settings true` is given after other security options. Closes [#1149]. - Fix `include_dir` not sorting config files before loading. This was partially fixed in 1.5 previously. - Improve documentation around the `include_dir` option. Closes [#1154]. - Fix case where old unreferenced msg_store messages were being saved to the persistence file, bloating its size unnecessarily. Closes [#389]. ## Library - Fix `mosquitto_topic_matches_sub()` not returning MOSQ_ERR_INVAL for invalid subscriptions like `topic/#abc`. This only affects the return value, not the match/no match result, which was already correct. ## Build - Don't require C99 compiler. - Add rewritten build test script and remove some build warnings. [#389]: https://github.com/eclipse/mosquitto/issues/389 [#1149]: https://github.com/eclipse/mosquitto/issues/1149 [#1154]: https://github.com/eclipse/mosquitto/issues/1154