We make a copy of the front buffer to render from. We do this so that we can render from the copy and let the sim thread do it's thing in parallel.
Making big changes. One thread is spawned, gets world context, prints it's dimensions.
No real processing done by the thread yet, need to tighten up some functions first for proper lock/unlocking.
Spawned now quits when the main thread wants to quit so we don't hang waiting for thread to join like in last commit.