better cleanup for ZoomBar and PanZoomBar. Fixes a memory leak.

r=crschmidt (closes #1949)


git-svn-id: http://svn.openlayers.org/trunk/openlayers@9113 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Control/PanZoom.js

@@ -54,11 +54,7 @@ OpenLayers.Control.PanZoom = OpenLayers.Class(OpenLayers.Control, {
      */
     destroy: function() {
         OpenLayers.Control.prototype.destroy.apply(this, arguments);
-        while(this.buttons.length) {
-            var btn = this.buttons.shift();
-            btn.map = null;
-            OpenLayers.Event.stopObservingElement(btn);
-        }
+        this.removeButtons();
         this.buttons = null;
         this.position = null;
     },
@@ -135,6 +131,28 @@ OpenLayers.Control.PanZoom = OpenLayers.Class(OpenLayers.Control, {
         return btn;
     },
     
+    /**
+     * Method: _removeButton
+     * 
+     * Parameters:
+     * btn - {Object}
+     */
+    _removeButton: function(btn) {
+        OpenLayers.Event.stopObservingElement(btn);
+        btn.map = null;
+        this.div.removeChild(btn);
+        OpenLayers.Util.removeItem(this.buttons, btn);
+    },
+    
+    /**
+     * Method: removeButtons
+     */
+    removeButtons: function() {
+        for(var i=this.buttons.length-1; i>=0; --i) {
+            this._removeButton(this.buttons[i]);
+        }
+    },
+    
     /**
      * Method: doubleClick
      *