code review 5656048: runtime, syscall, os/signal: fix windows build

src/pkg/os/signal/signal_unix.go

 // 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 darwin freebsd linux netbsd openbsd
+// +build darwin freebsd linux netbsd openbsd windows
 
 package signal
 
 import (
         "os"
         "syscall"
 )
 
 // In assembly.
 func signal_enable(uint32)
@@ skipping 13 matching lines @@
 func enableSignal(sig os.Signal) {
         switch sig := sig.(type) {
         case nil:
                 signal_enable(^uint32(0))
         case syscall.Signal:
                 signal_enable(uint32(sig))
         default:
                 // Can ignore: this signal (whatever it is) will never come in.
         }
 }