Bump github.com/google/certificate-transparency-go to v1.0.21

vendor/github.com/google/certificate-transparency-go/x509/ptr_sysptr_windows.go

@@ -0,0 +1,20 @@
+// Copyright 2018 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 go1.11
+
+package x509
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// For Go versions >= 1.11, the ExtraPolicyPara field in
+// syscall.CertChainPolicyPara is of type syscall.Pointer.  See:
+//   https://github.com/golang/go/commit/4869ec00e87ef
+
+func convertToPolicyParaType(p unsafe.Pointer) syscall.Pointer {
+	return (syscall.Pointer)(p)
+}