Revert back to merge sort for geometry sorting.

Some issues have been reported, and are difficult to track as they happen randomly.

jme3-core/src/main/java/com/jme3/renderer/queue/GeometryList.java

@@ -33,7 +33,7 @@ package com.jme3.renderer.queue;
 
 import com.jme3.renderer.Camera;
 import com.jme3.scene.Geometry;
-import com.jme3.util.ListSort;
+import com.jme3.util.SortUtil;
 
 /**
  * This class is a special purpose list of {@link Geometry} objects for render
@@ -48,7 +48,7 @@ public class GeometryList {
     private static final int DEFAULT_SIZE = 32;
 
     private Geometry[] geometries;
-    private ListSort listSort;
+    private Geometry[] geometries2;
     private int size;
     private GeometryComparator comparator;
 
@@ -61,8 +61,8 @@ public class GeometryList {
     public GeometryList(GeometryComparator comparator) {
         size = 0;
         geometries = new Geometry[DEFAULT_SIZE];
+        geometries2 = new Geometry[DEFAULT_SIZE];
         this.comparator = comparator;
-        listSort = new ListSort<Geometry>();
     }
 
     public void setComparator(GeometryComparator comparator) {
@@ -118,6 +118,8 @@ public class GeometryList {
             Geometry[] temp = new Geometry[size * 2];
             System.arraycopy(geometries, 0, temp, 0, size);
             geometries = temp; // original list replaced by double-size list
+
+            geometries2 = new Geometry[size * 2];
         }
         geometries[size++] = g;
     }
@@ -139,10 +141,10 @@ public class GeometryList {
     public void sort() {
         if (size > 1) {
             // sort the spatial list using the comparator
-            if(listSort.getLength() != size){
-                listSort.allocateStack(size);
-            }                       
-            listSort.sort(geometries,comparator);
+            System.arraycopy(geometries, 0, geometries2, 0, size);
+            SortUtil.msort(geometries2, geometries, 0, size-1, comparator);
+
+
         }
     }
 }