When using ChunkWorx to generate multiple chunks, the server would sometimes fail an assert because it would generate a chunk even when it was successfully loaded. This was caused by chunks queued in cWorld's m_SetChunkDataQueue and thus being marked as "InQueue" although they were already loaded.
Solved by adding a new parameter to chunk coord callbacks specifying whether the operation succeeded or failed, and using that instead of the chunk presence flag to decide whether to generate or not.
Made cSpawnPrepare execute on the same thread since it is a syncronous operation, and most of the code happens on the lighting thread.
Also moved cSpawnPrepare into its own file
