Saving issues in chunks that unload

[Drayux]

Hello! This is the first of a couple bugs I will report on this. Basically what goes on is that for any changes I make to a chunk, if that chunk is unloaded shortly afterward, more often than not, the changes I made will not be saved. If I should add any more information, let me know and I will add it, but that is the general description of what is going on. There is no crashes associated with it, but some of the time I will also only see the loss of data after reloading or exiting.

[kvverti]

This is caused by the server not saving chunks in time when the game closes, causing queued chunks to be thrown away (see #11 )

[cuchaz]

This might also have been caused by some broken IO thread synchronization, which I just fixed in 93af916