Allow MQTT topics longer than 32 chars

[schildbach]

My MQTT naming scheme (with mostly Tasmota clients) would require the topic name:

cmnd/studio/desk/strip/light/POWER

That's 34 characters.

[blazoncek]

You need to custom compile and use appropriate override.

-D MQTT_MAX_TOPIC_LEN=64 and -D MQTT_MAX_SERVER_LEN=64