patch for #556 - give the map object its own unique ID

git-svn-id: http://svn.openlayers.org/trunk/openlayers@2875 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Map.js

@@ -30,6 +30,9 @@ OpenLayers.Map.prototype = {
         "mouseout", "mousemove", "dragstart", "drag", "dragend",
         "changebaselayer"],
 
+    /** @type String */
+    id: null,
+    
     /** @type OpenLayers.Events */
     events: null,
 
@@ -153,6 +156,9 @@ OpenLayers.Map.prototype = {
         //set the default options
         this.setOptions(options);
 
+        this.id = OpenLayers.Util.createUniqueID("OpenLayers.Map_");
+
+
         this.div = div = OpenLayers.Util.getElement(div);
 
         // the viewPortDiv is the outermost div we modify