Clean up World.getPlayers().

Original idea from CyberTiger, PR #150

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

@@ -721,18 +721,15 @@ public class CraftWorld implements World {
     }
 
     public List<Player> getPlayers() {
-        List<Player> list = new ArrayList<Player>();
+        List<Player> list = new ArrayList<Player>(world.players.size());
 
-        for (Object o : world.entityList) {
+        for (EntityHuman human : world.players) {
-            if (o instanceof net.minecraft.server.Entity) {
+            HumanEntity bukkitEntity = human.getBukkitEntity();
-                net.minecraft.server.Entity mcEnt = (net.minecraft.server.Entity) o;
-                Entity bukkitEntity = mcEnt.getBukkitEntity();
 
             if ((bukkitEntity != null) && (bukkitEntity instanceof Player)) {
                 list.add((Player) bukkitEntity);
             }
         }
-        }
 
         return list;
     }