rebase: vendor golang.org/x/crypto and update to latest

The new SecretsMetadataKMS provider encrypts/decrypts DEKs as they are
stored in the metadata of volumes. The encryption/decryption uses
golang.org/x/crypto/scrypt to generate the encryption key from a
passphrase.

While vendoring golang.org/x/crypto, already vendored sub-packages have
been updated.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

vendor/golang.org/x/sys/plan9/race.go

@@ -0,0 +1,30 @@
+// Copyright 2012 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 plan9,race
+
+package plan9
+
+import (
+	"runtime"
+	"unsafe"
+)
+
+const raceenabled = true
+
+func raceAcquire(addr unsafe.Pointer) {
+	runtime.RaceAcquire(addr)
+}
+
+func raceReleaseMerge(addr unsafe.Pointer) {
+	runtime.RaceReleaseMerge(addr)
+}
+
+func raceReadRange(addr unsafe.Pointer, len int) {
+	runtime.RaceReadRange(addr, len)
+}
+
+func raceWriteRange(addr unsafe.Pointer, len int) {
+	runtime.RaceWriteRange(addr, len)
+}