vendor golang.org/x/crypto using glide

This would help us build go-mtree on RHEL/CentOS and
distros where golang.org/x/crypto isn't provided or supported.

Signed-off-by: Lokesh Mandvekar <lsm5@fedoraproject.org>

vendor/golang.org/x/crypto/hkdf/example_test.go

@@ -0,0 +1,61 @@
+// Copyright 2014 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 hkdf_test
+
+import (
+	"bytes"
+	"crypto/rand"
+	"crypto/sha256"
+	"fmt"
+	"golang.org/x/crypto/hkdf"
+	"io"
+)
+
+// Usage example that expands one master key into three other cryptographically
+// secure keys.
+func Example_usage() {
+	// Underlying hash function to use
+	hash := sha256.New
+
+	// Cryptographically secure master key.
+	master := []byte{0x00, 0x01, 0x02, 0x03} // i.e. NOT this.
+
+	// Non secret salt, optional (can be nil)
+	// Recommended: hash-length sized random
+	salt := make([]byte, hash().Size())
+	n, err := io.ReadFull(rand.Reader, salt)
+	if n != len(salt) || err != nil {
+		fmt.Println("error:", err)
+		return
+	}
+
+	// Non secret context specific info, optional (can be nil).
+	// Note, independent from the master key.
+	info := []byte{0x03, 0x14, 0x15, 0x92, 0x65}
+
+	// Create the key derivation function
+	hkdf := hkdf.New(hash, master, salt, info)
+
+	// Generate the required keys
+	keys := make([][]byte, 3)
+	for i := 0; i < len(keys); i++ {
+		keys[i] = make([]byte, 24)
+		n, err := io.ReadFull(hkdf, keys[i])
+		if n != len(keys[i]) || err != nil {
+			fmt.Println("error:", err)
+			return
+		}
+	}
+
+	// Keys should contain 192 bit random keys
+	for i := 1; i <= len(keys); i++ {
+		fmt.Printf("Key #%d: %v\n", i, !bytes.Equal(keys[i-1], make([]byte, 24)))
+	}
+
+	// Output:
+	// Key #1: true
+	// Key #2: true
+	// Key #3: true
+}