[Fix] Determine that IPAddress.IPv6Any is a local IP address if available

Fix for pull request #243.

websocket-sharp/Ext.cs

@@ -1297,9 +1297,20 @@ namespace WebSocketSharp
       if (address == null)
         return false;
 
-      if (address.Equals (System.Net.IPAddress.Any) || System.Net.IPAddress.IsLoopback (address))
+      if (address.Equals (System.Net.IPAddress.Any))
         return true;
 
+      if (address.Equals (System.Net.IPAddress.Loopback))
+        return true;
+
+      if (Socket.OSSupportsIPv6) {
+        if (address.Equals (System.Net.IPAddress.IPv6Any))
+          return true;
+
+        if (address.Equals (System.Net.IPAddress.IPv6Loopback))
+          return true;
+      }
+
       var host = System.Net.Dns.GetHostName ();
       var addrs = System.Net.Dns.GetHostAddresses (host);
       foreach (var addr in addrs)