icmp: add support for windows

Fixes #9253

Change-Id: I29ad04698e20c6e4d04a2b5b161693ac7cd482a2

icmp/helper_unix.go → icmp/helper_posix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris windows
 
 package icmp
 

icmp/listen_unix.go → icmp/listen_posix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris windows
 
 package icmp
 

icmp/listen_stub.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build nacl plan9 windows
+// +build nacl plan9
 
 package icmp