Update dependencies for 1.18.0 release (#1175)

vendor/golang.org/x/sys/internal/unsafeheader/unsafeheader.go

@@ -0,0 +1,30 @@
+// Copyright 2020 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 unsafeheader contains header declarations for the Go runtime's
+// slice and string implementations.
+//
+// This package allows x/sys to use types equivalent to
+// reflect.SliceHeader and reflect.StringHeader without introducing
+// a dependency on the (relatively heavy) "reflect" package.
+package unsafeheader
+
+import (
+	"unsafe"
+)
+
+// Slice is the runtime representation of a slice.
+// It cannot be used safely or portably and its representation may change in a later release.
+type Slice struct {
+	Data unsafe.Pointer
+	Len  int
+	Cap  int
+}
+
+// String is the runtime representation of a string.
+// It cannot be used safely or portably and its representation may change in a later release.
+type String struct {
+	Data unsafe.Pointer
+	Len  int
+}