fix util.inspect(new Error(..)) for IE

IE is stupid and adds enumerable fields

Author: defunctzombie

util.js

@@ -239,6 +239,13 @@ function formatValue(ctx, value, recurseTimes) {
     keys = Object.getOwnPropertyNames(value);
   }
 
+  // IE doesn't make error fields non-enumerable
+  // http://msdn.microsoft.com/en-us/library/ie/dww52sbt(v=vs.94).aspx
+  if (isError(value)
+      && (keys.indexOf('message') >= 0 || keys.indexOf('description') >= 0)) {
+    return formatError(value);
+  }
+
   // Some type of object without properties can be shortcutted.
   if (keys.length === 0) {
     if (isFunction(value)) {