Finish 4.8.1

重新发布 4.8.1
本次重发布修复上次发布时libsscrypto版本错误导致的问题
--------------------
添加 auth_chain_e/f
添加 Xchacha20 Xsalsa20 支持
更新 libsodium 到 v1.0.13

Author: Akkariiin

shadowsocks-csharp/Controller/UpdateChecker.cs

@@ -21,7 +21,7 @@ public class UpdateChecker
 
         public const string Name = "ShadowsocksR";
         public const string Copyright = "Copyright © BreakWa11 2017. Fork from Shadowsocks by clowwindy";
-        public const string Version = "4.8.0";
+        public const string Version = "4.8.1";
 #if !_DOTNET_4_0
         public const string NetVer = "2.0";
 #elif !_CONSOLE