Build fix for go1.11rc1 (#6354)

Vendorized the following packages

- "github.com/rjeczalik/notify"
- "github.com/minio/highwayhash"

Fixes #6315

vendor/github.com/rjeczalik/notify/watcher_fsevents_go1.11.go

@@ -0,0 +1,9 @@
+// Copyright (c) 2018 The Notify Authors. All rights reserved.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+// +build darwin,!kqueue,go1.11
+
+package notify
+
+const refZero = 0