Peter M. Groen / FlashMQ

Fix websocket crash case

Fix infinite loop on lying about websocket frame sizes

This fixes infinite loops when you send a frame type that is not handled.

And check Qos.

When sending many 0xFF, it would overflow.

Found by using afl-fuzz.

This allows creation of multiple listeners, with different protocols
and/or SSL certificates.

Related change: settings is now a class that is copyable and assignable,
and is done so to each thread on reload.

Semi-related fix: fix crash in quit when multiple threads initiated it.
This came to light when testing the auth plugin settings.

And fixed an assert in CirBuf.read().

It's also used to reload settings. Settings are copied to threads, to
avoid concurrency issues.

Also changed the disconnect reason a little: it now shows them all, so I
don't have to worry about which one is more important.

And some side issues.

And include some extra error conditions.

It also contains some related improvements that I needed:

* Show disconnect reason
* Fix the while condition for doing write() to avoid an unnecessary call
* Config reloading logic

Also includes fixes to packet parsing that I couldn't make a separate
commit for.

When it comes to QoS 1, these things are still left, off the top of my
head:

- vector for qos queue? It helps with ordering and is CPU cache friendly.
- Store subscription QoS.
- Do retained messages have QoS?
- Give session client's name, to access it later.

Also reloading of settings, which re-opens the log file.

There still is a bug: writing a very big packet. I wrote the test case
already.

Also materializes some concepts about MqttPacket.

Roughly...