THRIFT-4609 keep InnerException wherever appropriate
Client: C#
Patch: Jens Geyer

This closes #1576
diff --git a/lib/csharp/src/TException.cs b/lib/csharp/src/TException.cs
index 35193c5..aa9a210 100644
--- a/lib/csharp/src/TException.cs
+++ b/lib/csharp/src/TException.cs
@@ -31,8 +31,8 @@
         {
         }
 
-        public TException(string message)
-            : base(message)
+        public TException(string message, Exception inner)
+            : base(message, inner)
         {
         }