add Vector.destroyFeatures() and call it from WFS.moveTo(), which keeps WFS

from loading the same set of features multiple times. Includes tests. fixes
#622.



git-svn-id: http://svn.openlayers.org/trunk/openlayers@2996 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Vector.js

@@ -262,6 +262,14 @@ OpenLayers.Layer.Vector.prototype =
         }
     },
 
+    /**
+     */
+    destroyFeatures: function () {
+        for (var i = this.features.length - 1; i >= 0; i--) {
+            this.features[i].destroy();
+        }
+    },
+
     /**
      * @param {String} fid
      * @param {Object} style

lib/OpenLayers/Layer/WFS.js

@@ -188,6 +188,7 @@ OpenLayers.Layer.WFS.prototype =
                 this.tile.draw();
             } else {
                 if (this.vectorMode) {
+                    this.destroyFeatures();
                     this.renderer.clear();
                 } else {
                     this.clearMarkers();