Add a option to disable entity update

src/minecraft/net/minecraft/src/Constants.java

@@ -7,7 +7,8 @@ public class Constants {
 	public static       boolean DISABLE_MODULO = false,
 								ENABLE_FRINGE_LAND = false,
 								FLOAT_PERLIN_GENERATOR = false,
-								COMPILE_CHUNK_ASYNC = false;
+								COMPILE_CHUNK_ASYNC = false,
+								DISABLE_ENTITY_UPDATE = false;
 	
 	@Deprecated(/* forRemoval = true */)
 	public static boolean USE_64BIT_PERLIN_GENERATOR = false;

src/minecraft/net/minecraft/src/World.java

@@ -295,8 +295,9 @@ public abstract class World implements IBlockAccess
      */
     public boolean doChunksNearChunkExist(BigInteger par1, int par2, BigInteger par3, int par4)
     {
-    	return true;
-//        return this.checkChunksExist(par1 - par4, par2 - par4, par3 - par4, par1 + par4, par2 + par4, par3 + par4);
+//    	return true;
+    	BigInteger dist = BigInteger.valueOf(par4);
+        return this.checkChunksExist(par1.subtract(par3), par2 - par4, par3.subtract(dist), par1.add(dist), par2 + par4, par3.add(dist));
     }
 
     /**
@@ -1759,6 +1760,7 @@ public abstract class World implements IBlockAccess
         for (var1 = 0; var1 < this.loadedEntityList.size(); ++var1)
         {
             var2 = (Entity)this.loadedEntityList.get(var1);
+            if (!(var2 instanceof EntityPlayer) && Constants.DISABLE_ENTITY_UPDATE) continue;
 
             if (var2.ridingEntity != null)
             {