Peter M. Groen / FlashMQ

This entails making copies of the original packet when necessary,
because QoS 0 doesn't have a packet id. I tried to keep it to an
absolute minimum and do some precarious optmizations for it. There are
tests though.

Three parts to it:

- Start the app fresh per test. This avoids annoyances like getting
  retained messages on subscribe, messing up the test.
- Waiting for suback was apparently necessary.
- Because the Qt event loop was given time, waiting for publishes was
  sometimes pointless because it had already arrived. So, checking the
  receive list first.

The MQTT docs showed a wrong condition for checking malformed packets.

And, we have to grow buffers to MAX_PACKET_SIZE, otherwise we can't
process. I still have some inteligent buffer shrink logic in mind.

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