Peter M. Groen / FlashMQ

And fix off-by-one error.

It merely drops packets when they exceed it. The specs are unclear about
whether you're supposed to delay transmission until the quota is
non-negative again. I decided against it because of increased
complexity, and because on a continously overloaded client, this makes
no sense.

Effectively, this formalizes the 'max qos pending' mechanism that was
already in place.

It also includes PUBACK/PUBREL/PUBCOMP error handling, because that
needed to be done for proper quota control.

Most of it is limits we already implemented non-standard compliant.

This saves some allocations.

This also meant having to set the C++ standard to 2014.

The getCopy() methods of sessions and mqttpackets can't be changed,
because of access errors (private).

This mutes all INFO and NOTICE.

Also fixed the parsing of the log_subscriptions.

Files are simple serialized bytes prefaced by lengths. File is hashed to
verify integrity. This was also a good way preventing unexpected errors
when trying to crash the parser by having it load a different file.

This change includes some refactoring that was necessary:

- It 'fixes' looking at the wrong thread's authentiction. This is still
  wrong though. It will be fixed by a thread local pointer in the next
  commit.
- Deadlocks with yourself are handled in rwlockguard.
- QoSPacketQueue is now a class.
- Probably other tweaks.

https://github.com/halfgaar/FlashMQ/issues/2

Found by quinox using AFL.

Encrypted version only.

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

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 some side issues.

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

It can be defined in the config file, along with options.