Massage util.inherits for perf increase

lib/util.js

@@ -423,6 +423,11 @@ exports.pump = function(readStream, writeStream, callback) {
 exports.inherits = function(ctor, superCtor) {
   ctor.super_ = superCtor;
   ctor.prototype = Object.create(superCtor.prototype, {
-    constructor: { value: ctor, enumerable: false }
+    constructor: {
+      value: ctor,
+      enumerable: false,
+      writable: true,
+      configurable: true
+    }
   });
 };