all: Add filesystem notification support

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3986

vendor/github.com/zillode/notify/watchpoint_other.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2014-2015 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 !windows
+
+package notify
+
+// eventmask uses ei to create a new event which contains internal flags used by
+// notify package logic.
+func eventmask(ei EventInfo, extra Event) Event {
+	return ei.Event() | extra
+}
+
+// matches reports a match only when:
+//
+//   - for user events, when event is present in the given set
+//   - for internal events, when additionally both event and set have omit bit set
+//
+// Internal events must not be sent to user channels and vice versa.
+func matches(set, event Event) bool {
+	return (set&omit)^(event&omit) == 0 && set&event == event
+}