decompose the marker destruction code out so that it can be overridden in subclasses

git-svn-id: http://svn.openlayers.org/trunk/openlayers@1497 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Feature.js

@@ -63,7 +63,7 @@ OpenLayers.Feature.prototype= {
         this.lonlat = null;
         this.data = null;
         if (this.marker != null) {
-            this.marker.destroy();
+            this.destroyMarker(this.marker);
             this.marker = null;
         }
         if (this.popup != null) {
@@ -89,6 +89,10 @@ OpenLayers.Feature.prototype= {
         return this.marker;
     },
 
+    destroyMarker: function() {
+        this.marker.destroy();  
+    },
+
     /**
      * 
      */