POC Distant landscape mesh clipping - alpha rejection

Hard-coded alpha rejection of LOD texture around cell (12,1) for testing. As can be seen, the clipping with the terrain is gone (yay!) but now there are ugly seams between the terrain and low-poly LOD mesh at the boundary. Will need to experiment with alpha blending to see if that works better at the edges. The view distance was also increased to just under 90000 and the fog has been pushed back towards the mountains.