Update physics World in another Thread

[AntonioModer]

I found the main critical problem.
Functions in http://www.love2d.org/wiki/World:setCallbacks works only in one thread and they cant pass to another.
Same for http://www.love2d.org/wiki/Fixture:setUserData and http://www.love2d.org/wiki/Body:setUserData if userData is table or function (pointer).

[raidho36]

Well yeah - LÖVE threads are not real threads, because Lua doesn't support threads. They sort of are threads, but you need to keep in mind that they're implemented via separate Lua states running in separate threads. You can't pass a table (or anything really) from one Lua state to another, you can only do a full duplicate (so it won't be the same object, just a snapshot clone of it), which isn't even always possible.