THRIFT-2015 Thrift exceptions should derive from TException

Patch: Jens Geyer
diff --git a/lib/csharp/src/Protocol/TProtocolException.cs b/lib/csharp/src/Protocol/TProtocolException.cs
index 4e4393f..bc002d3 100644
--- a/lib/csharp/src/Protocol/TProtocolException.cs
+++ b/lib/csharp/src/Protocol/TProtocolException.cs
@@ -25,7 +25,7 @@
 
 namespace Thrift.Protocol
 {
-	public class TProtocolException : Exception
+	public class TProtocolException : TException
 	{
 		public const int UNKNOWN = 0;
 		public const int INVALID_DATA = 1;