Asynchronous tasks

[xoft]

There's no simple way to limit the thread's interaction with the rest of the server. As long as there's cRoot:Get():GetWorld() and similar functions, the worker thread could always interact with the main server with disastrous results.
On the other hand, if we remove the entire API form the thread's Lua state, then the thread cannot do any work at all - it wouldn't know how to interact with a cBlockArea and so on.