Added getHighestBlockYAt

src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -42,6 +42,10 @@ public class CraftWorld implements World {
 
         return block;
     }
+    
+    public int getHighestBlockYAt(int x, int z) {
+    	return world.d(x, z);
+    }
 
     public Chunk getChunkAt(int x, int z) {
         ChunkCoordinate loc = new ChunkCoordinate(x, z);