This allows other threads to notify the main thread to wake it up while it's sleeping between ticks, allowing reduction of processing latency.
Currently only RakLib and the CommandReader threads utilize this, but it's planned to extend it to more things in the near future.
CommandReader is now event-driven instead of poll-based - the server will not poll the CommandReader thread for messages each tick anymore.
RakLib utilizes this mechanism to get packets processed without delays to lower latency.
This now adds an extra dependency - `pocketmine/snooze` library contains the meat of the code used for this. See the Snooze repository for details.
this needs further changes (particularly to Furnace) to stop things abusing NBT for runtime data handling, otherwise performance is going to drop off a cliff.
Since we don't use the PEAR-style namespacing convention, there's no reason to use PSR-0 autoloader.
We don't quite follow PSR-4 conventions because there is still a pocketmine subdirectory, but changing this might pollute the git history, so I'm wary of changing it.
This fix doesn't fix existing data, but it will prevent the bug happening in the future by capping the length of strings to 32767 bytes, and throwing an exception if too long.
