tempfork/registry: add golang.org/x/sys/windows/registry + CL 236681

Temporary fork of golang.org/x/sys/windows/registry with:

   windows/registry: add Key.WaitChange wrapper around RegNotifyChangeKeyValue
   https://go-review.googlesource.com/c/sys/+/236681

tempfork/registry/mksyscall.go

@@ -0,0 +1,9 @@
+// Copyright 2015 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 generate
+
+package registry
+
+//go:generate go run golang.org/x/sys/windows/mkwinsyscall -output zsyscall_windows.go syscall.go