Peter M. Groen / FlashMQ

This is way faster.

This should fix corruption. There were inexplicable stalls of timed
events, and the debugger showed the names were all corrupted. std::sort
can do that sort of thing, apparently.

And fix off-by-one error.

This implements the first testing version of MQTT5 support.

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.

The only thing it did was false trip the fuzzer.

Diff with 'ignore whitespace' looks clean.

This also contains some fixes/unifications for traditional
authentication, error handling specifically.

The CONACK indicated that it's not supported, and the specs say to issue
a disconnect when they're used after all.

This should prevent stale data from old clients from manipulating the
session.

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.

I didn't count the seconds it was already waiting. It does now.

This required a special type WillPublish to make this easier and more
logical.

It erroneously referred to the system function 'dup' now...

Also fix some bugs:

- The password can be binary data.
- The will topic is now also checked.

This is better in line with how the copy factory is meant to be used. It
actually broke on the assert on 'externallyReceived' before.

This allows easier saving of MQTT5 properties, for which a new file
version for retained messages is created. It uses the packet parsing logic.

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

It went over boundry when there were no properties.

Also changed will logic in disconnect: only clear it when it's a
successful disconnect.

- Delay is properly counted from moment of disconnect.
- When a session is picked up again, the will is not sent.
- An actual fix to what I tried a few commits ago: fix sending will
  twice.

This logic should make storing wills also easier.

I think it's very hard to distinguish between protocol error and
malformed packet. It's kind of arbitrary...

The loop of pending messages was stuck.

We saved a session expiry interval of 0. I may need to change that
session copying idea.