Fixed incorrect mask for determining fs.Stats types

lib/fs.js

@@ -11,7 +11,7 @@ var kPoolSize = 40*1024;
 fs.Stats = binding.Stats;
 
 fs.Stats.prototype._checkModeProperty = function (property) {
-  return ((this.mode & property) === property);
+  return ((this.mode & process.S_IFMT) === property);
 };
 
 fs.Stats.prototype.isDirectory = function () {

src/node_constants.cc

@@ -23,6 +23,7 @@ void DefineConstants(Handle<Object> target) {
   NODE_DEFINE_CONSTANT(target, O_WRONLY);
   NODE_DEFINE_CONSTANT(target, O_RDWR);
 
+  NODE_DEFINE_CONSTANT(target, S_IFMT);
   NODE_DEFINE_CONSTANT(target, S_IFREG);
   NODE_DEFINE_CONSTANT(target, S_IFDIR);
   NODE_DEFINE_CONSTANT(target, S_IFCHR);