Redstone fixes and improvements [SEE DESC]

Haha, see desc.

* Improved redstone speed through a marking dirty system. Only a select
few devices are still continuously simulated
* Fixed redstone crashing with recent piston changes

src/Chunk.cpp

@@ -1514,6 +1514,7 @@ void cChunk::FastSetBlock(int a_RelX, int a_RelY, int a_RelZ, BLOCKTYPE a_BlockT
 	}
 
 	MarkDirty();
+	m_IsRedstoneDirty = true;
 
 	m_ChunkData.SetBlock(a_RelX, a_RelY, a_RelZ, a_BlockType);