Delegate recreateStructures to nms provider. Fixes BUKKIT-2760

This was a miss when updating to 1.4.2

src/main/java/org/bukkit/craftbukkit/generator/InternalChunkGenerator.java

@@ -3,6 +3,6 @@ package org.bukkit.craftbukkit.generator;
 import net.minecraft.server.IChunkProvider;
 import org.bukkit.generator.ChunkGenerator;
 
+// Do not implement functions to this class, add to NormalChunkGenerator
 public abstract class InternalChunkGenerator extends ChunkGenerator implements IChunkProvider {
-    public void recreateStructures(int i, int j) {}
 }

src/main/java/org/bukkit/craftbukkit/generator/NormalChunkGenerator.java

@@ -69,6 +69,11 @@ public class NormalChunkGenerator extends InternalChunkGenerator {
         return provider.findNearestMapFeature(world, string, i, i1, i2);
     }
 
+    public void recreateStructures(int i, int j) {
+        provider.recreateStructures(i, j);
+    }
+
+    // n.m.s implementations always return 0. (The true implementation is in ChunkProviderServer)
     public int getLoadedChunks() {
         return 0;
     }