Optimise chunk set (#4260)

Closes #1244

Initially I was just going to add the cChunkData to cSetChunkData but profiling revealed 
that the copying wasn't even the biggest slowdown. Much more time was being spent in 
cChunk::CreateBlockEntities and cChunk::WakeUpSimulators than was in memcpy so I've made 
those significantly faster as well.

Optimisations performed:
 * cSetChunkData now stores blocks in a cChunkData object
 * cChunkData objects can now perform moves even if they are using different pools
 * cChunk::CreateBlockEntities now iterates in the correct order and only over present chunk sections
 * Similarly for cChunk::WakeUpSimulators
 * cSetChunkData::CalculateHeightMap now shortcuts to the highest present chunk section before checking blocks directly

src/ChunkMap.cpp

@@ -38,10 +38,8 @@
 cChunkMap::cChunkMap(cWorld * a_World) :
 	m_World(a_World),
 	m_Pool(
-		new cListAllocationPool<cChunkData::sChunkSection, 1600>(
-			std::unique_ptr<cAllocationPool<cChunkData::sChunkSection>::cStarvationCallbacks>(
-				new cStarvationCallbacks()
-			)
+		cpp14::make_unique<cListAllocationPool<cChunkData::sChunkSection>>(
+			cpp14::make_unique<cStarvationCallbacks>(), 1600u
 		)
 	)
 {