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/crypto/poly1305/bits_compat.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !go1.13
 // +build !go1.13
 
 package poly1305

vendor/golang.org/x/crypto/poly1305/bits_go1.13.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build go1.13
 // +build go1.13
 
 package poly1305

vendor/golang.org/x/crypto/poly1305/mac_noasm.go

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64,!ppc64le,!s390x gccgo purego
+//go:build (!amd64 && !ppc64le && !s390x) || !gc || purego
+// +build !amd64,!ppc64le,!s390x !gc purego
 
 package poly1305
 

vendor/golang.org/x/crypto/poly1305/sum_amd64.go

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo,!purego
+//go:build gc && !purego
+// +build gc,!purego
 
 package poly1305
 

vendor/golang.org/x/crypto/poly1305/sum_amd64.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo,!purego
+// +build gc,!purego
 
 #include "textflag.h"
 

vendor/golang.org/x/crypto/poly1305/sum_ppc64le.go

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo,!purego
+//go:build gc && !purego
+// +build gc,!purego
 
 package poly1305
 

vendor/golang.org/x/crypto/poly1305/sum_ppc64le.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo,!purego
+// +build gc,!purego
 
 #include "textflag.h"
 

vendor/golang.org/x/crypto/poly1305/sum_s390x.go

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo,!purego
+//go:build gc && !purego
+// +build gc,!purego
 
 package poly1305
 

vendor/golang.org/x/crypto/poly1305/sum_s390x.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo,!purego
+// +build gc,!purego
 
 #include "textflag.h"