windows/svc: add new package to help create and manage Windows services

Change-Id: I58bb446aaa387b31d8a9ff4217793a170b96a7e2
Reviewed-on: https://go-review.googlesource.com/9104
Reviewed-by: Rob Pike <r@golang.org>

windows/svc/example/beep.go

@@ -0,0 +1,22 @@
+// Copyright 2012 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 windows
+
+package main
+
+import (
+	"syscall"
+)
+
+// BUG(brainman): MessageBeep Windows api is broken on Windows 7,
+// so this example does not beep when runs as service on Windows 7.
+
+var (
+	beepFunc = syscall.MustLoadDLL("user32.dll").MustFindProc("MessageBeep")
+)
+
+func beep() {
+	beepFunc.Call(0xffffffff)
+}