events: loop backwards in removeListener

`removeAllListeners` is removing events from end to start. Therefore
it spends O(n^2) time, since `removeListener` is searching from start to
end.

lib/events.js

@@ -201,7 +201,7 @@ EventEmitter.prototype.removeListener = function(type, listener) {
       this.emit('removeListener', type, listener);
 
   } else if (typeof list === 'object') {
-    for (i = 0; i < length; i++) {
+    for (i = length; i-- > 0;) {
       if (list[i] === listener ||
           (list[i].listener && list[i].listener === listener)) {
         position = i;