expose map of pending queries in Util.response handler

so that we can more easily generate 'globally' unique identifiers

www/common/common-util.js

@@ -160,6 +160,7 @@
             },
             expect: expect,
             handle: handle,
+            _pending: pending,
         };
     };
 
@@ -187,6 +188,14 @@
             .toString(32).replace(/\./g, '');
     };
 
+    Util.guid = function (map) {
+        var id = Util.uid();
+        // the guid (globally unique id) is valid if it does already exist in the map
+        if (typeof(map[id]) === 'undefined') { return id; }
+        // otherwise try again
+        return Util.guid(map);
+    };
+
     Util.fixHTML = function (str) {
         if (!str) { return ''; }
         return str.replace(/[<>&"']/g, function (x) {