safesocket: add WindowsLocalPort const

Remove all the 41112 references.

Change-Id: I2d7ed330d457e3bb91b7e6416cfb2667611e50c4
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

safesocket/safesocket.go

@@ -13,6 +13,10 @@ import (
 	"time"
 )
 
+// WindowsLocalPort is the default localhost TCP port
+// used by safesocket on Windows.
+const WindowsLocalPort = 41112
+
 type closeable interface {
 	CloseRead() error
 	CloseWrite() error