os: new FileInfo, FileMode types + update tree

R=golang-dev, r, r, gri, bradfitz, iant, iant, nigeltao, n13m3y3r
CC=golang-dev
https://golang.org/cl/5416060
diff --git a/src/pkg/os/export_test.go b/src/pkg/os/export_test.go
new file mode 100644
index 0000000..29f0511
--- /dev/null
+++ b/src/pkg/os/export_test.go
@@ -0,0 +1,10 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+// Export for testing.
+
+var TimespecToTime = timespecToTime
+var Atime = atime