This is a bugfix release. ## Broker - Fix persistent clients being incorrectly expired on Raspberry Pis. Closes [#1272]. - Windows: Allow other applications access to the log file when running. Closes [#515]. - Fix incoming QoS 2 messages being blocked when `max_inflight_messages` was set to 1. Closes [#1332]. - Fix incoming messages not being removed for a client if the topic being published to does not have any subscribers. Closes [#1322]. ## Client library - Fix MQTT v5 subscription options being incorrectly set for MQTT v3 subscriptions. Closes [#1353]. - Make behaviour of `mosquitto_connect_async()` consistent with `mosquitto_connect()` when connecting to a non-existent server. Closes [#1345]. - `mosquitto_string_option(mosq, MOSQ_OPT_TLS_KEYFORM, ...)` was incorrectly returning `MOSQ_ERR_INVAL` with valid input. This has been fixed. Closes [#1360]. - `on_connect` callback is now called with the correct v5 reason code if a v5 client connects to a v3.x broker and is sent a CONNACK with the "unacceptable protocol version" connack reason code. - Fix memory leak when setting v5 properties in `mosquitto_connect_v5()`. - Fix properties not being sent on QoS>0 PUBLISH messages. ## Clients - `mosquitto_pub`: fix error codes not being returned when `mosquitto_pub` exits. Closes [#1354]. - All clients: improve error messages when connecting to a v3.x broker when in v5 mode. Closes [#1344]. ## Other - Various documentation fixes. [#515]: https://github.com/eclipse/mosquitto/issues/515 [#1272]: https://github.com/eclipse/mosquitto/issues/1272 [#1322]: https://github.com/eclipse/mosquitto/issues/1322 [#1332]: https://github.com/eclipse/mosquitto/issues/1332 [#1344]: https://github.com/eclipse/mosquitto/issues/1344 [#1345]: https://github.com/eclipse/mosquitto/issues/1345 [#1353]: https://github.com/eclipse/mosquitto/issues/1353 [#1354]: https://github.com/eclipse/mosquitto/issues/1354 [#1360]: https://github.com/eclipse/mosquitto/issues/1360