documenting that Layer.VirtualEarth requires restrictedExtent to be set, and changing the examples accordingly. p=marcjansen (closes #3123)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@11503 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/VirtualEarth.js

@@ -13,7 +13,11 @@
 
 /**
  * Class: OpenLayers.Layer.VirtualEarth
- * 
+ * Instances of OpenLayers.Layer.VirtualEarth are used to display the data from
+ *     the Bing Maps AJAX Control (see e.g. 
+ *     http://msdn.microsoft.com/library/bb429619.aspx). Create a VirtualEarth 
+ *     layer with the <OpenLayers.Layer.VirtualEarth> constructor.
+ *     
  * Inherits from:
  *  - <OpenLayers.Layer.EventPane>
  *  - <OpenLayers.Layer.FixedZoomLevels>
@@ -94,6 +98,22 @@ OpenLayers.Layer.VirtualEarth = OpenLayers.Class(
 
     /** 
      * Constructor: OpenLayers.Layer.VirtualEarth
+     * Creates a new instance of a OpenLayers.Layer.VirtualEarth. If you use an
+     *     instance of OpenLayers.Layer.VirtualEarth in you map, you should set 
+     *     the <OpenLayers.Map> option restrictedExtent to a meaningful value,
+     *     e.g.:
+     * (code)
+     * var map = new OpenLayers.Map( 'map', {
+     *     // other map options
+     *     restrictedExtent : OpenLayers.Bounds(-20037508, -20037508, 20037508, 20037508)
+     * } );
+     * 
+     * var veLayer = new OpenLayers.Layer.VirtualEarth (
+     *     "Virtual Earth Layer"
+     * );
+     * 
+     * map.addLayer( veLayer );
+     * (end)
      * 
      * Parameters:
      * name - {String}