Vendor code using godep.

For 3rd parties building binary packages, and for build consistency in
general, it is very helpful to have the same set of dependencies at
any time the product is built.

See [tools/godep](https://github.com/tools/godep) for further details.

vendor/golang.org/x/sys/unix/constants.go

@@ -0,0 +1,13 @@
+// Copyright 2015 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.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package unix
+
+const (
+	R_OK = 0x4
+	W_OK = 0x2
+	X_OK = 0x1
+)