Add avltree.js version 6ffd3f2917.

static/js/libs/avltree.js

@@ -41,7 +41,7 @@
  * - reverseOrderTraverse   O(logn + k), where k is number of traversed nodes
  * </pre>
  */
-
+// Version 6ffd3f2917d32c28a6651644843edb979b42c3f0
 
 // Compatibility code to run standalone.
 (function(root) {
@@ -836,4 +836,4 @@ AvlTree.Node.prototype.isLeftChild = function() {
 // Return as global.
 root.AvlTree = AvlTree;
 
-}(window));
+}(window));