Peter M. Groen / FlashMQ

This also adds configuration options for choosing what address to bind
to.

Found by fuzzing.

Probably I also need a flag to fake already being upgraded, because
otherwise we never get passed the complicated websocket handshake.

And check Qos.

This can be called by a fuzzer like afl-fuzz.

When sending many 0xFF, it would overflow.

Found by using afl-fuzz.

This fixes the 100ms wait time requirement.

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().

The ping/pong is actually untested at this point, because Paho (my test
client for now) doesn't do those. I wonder if any do, because MQTT
already has ping/pong.

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.

This includes a timer mechanism.

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

Connected to this is preventing duplicate subscriptions. It's a bit
unclear what to do when you get a subscription for the same topic with a
different QoS? Change the Qos? Ignore?

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.