this was previously part of the abandoned package pocketmine/spl. It had to be separated in the PM3 days, because RakLib depended on it.
Since RakLib 0.13, RakLib stopped being dependent on or aware of pthreads, so it no longer depends on any thread-related packages.
It's also possible to absorb pocketmine/snooze and pocketmine/classloader back into the core with this in mind.
I previously avoided this due to being unsure of the effects; however, it's clear that we already use typed properties on Threaded things in other places anyway, and the only known issues are with uninit properties, and arrays.
this gains a very small performance improvement by avoiding unnecessary !== null checks on every packet written in either direction. It's insignificant for sure, but I just found this code in an old stash, so what the heck.
at this point it's really not much more than just a thread-safe way to transmit parameters from main to thread. Maybe we can ditch it in favour of a generic closure-based thread implementation.
