SelectFeature control can now select across multiple vector

layers when passed an array of layers instead of a single layer with 
the constructor. This changeset also introduces a new layer type, 
Layer.Vector.RootContainer, which will be set as the topmost layer by 
the SelectFeature control and collect the svg/vml/canvas roots of 
multiple vector layers. r=crschmidt (closes #1666)


git-svn-id: http://svn.openlayers.org/trunk/openlayers@9116 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Vector.js

@@ -445,6 +445,23 @@ OpenLayers.Layer.Vector = OpenLayers.Class(OpenLayers.Layer, {
             }
         }    
     },
+    
+    /** 
+     * APIMethod: display
+     * Hide or show the Layer
+     * 
+     * Parameters:
+     * display - {Boolean}
+     */
+    display: function(display) {
+        OpenLayers.Layer.prototype.display.apply(this, arguments);
+        // we need to set the display style of the root in case it is attached
+        // to a foreign layer
+        var currentDisplay = this.div.style.display;
+        if(currentDisplay != this.renderer.root.style.display) {
+            this.renderer.root.style.display = currentDisplay;
+        }
+    },
 
     /**
      * APIMethod: addFeatures