LC2H V4.2.4-LTS

Fixed the Distant Horizons V3.3.0 crash and sorted another annoying worldgen stall :]

• DH compatibility no longer directly loads its mixin accessor, which was causing an IllegalClassLoadError. The thread check is now looked up lazily, and the DH mixin targets the right chunk method. #22
• Floating-block cleanup now checks that neighboring chunks are loaded before updating blocks. If they aren’t, it requeues the work instead of forcing a blocking chunk load on the server thread. #21