Peter M. Groen / FlashMQ

Check events are placed in a sorted map based on the last activity and
keep-alive interval of the client.

This makes it more accurate and reduces system load because it saves
unnecessary checking.

On server shutdown and when taking over a session.

On disconnect, wills are queued first, we wait for the queueing to be done, then
initiate disconnect.

When TCP buffers are full and fds are not reported by epoll, the thread
loop still exits and clients are just closed on exit.

This includes some logic to have threads finish their work before
quitting.

One fix is client destruction happening on the correct thread (when
kicking another one off with existing client ID). This caused deadlocks
on the subscriptions lock during a race condition when
doKeepAliveCheck() also ran.

A related deadlock was that the queued functions were executed while
holding the lock taskQueueMutex. Together with the subscriptions lock,
that was executed in the $SYS topic function, this also caused
deadlocks.

This avoids changing which thread runs the code.

Also let auth_plugin_serialize_init affect cleanup serialization.

It was a mistake that it ran inside the timer thread, which came to
light by asserting the thread local authentication pointer (see a few
commits ago).

Also include a few stats.

Instead of getting it from the sender of a packet. Sometimes there was
no sender.

This fixes a crash on retained messages, because those newly created
packets didn't have a sender to get the threaddata from. So, using a
special object for it is easier and more robust.

Encrypted version only.

My IDE didn't understand them for finding symbols, apparently.

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.

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

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

We use epoll now to change readiness.

I put the main app in a seperate class for it, because it was easier.

Roughly...

And I had to fix a threading bug.