THRIFT-2506 Update TProtocolException error codes to be used consistently throughout the library

Patch: Jens Geyer
diff --git a/lib/csharp/src/Protocol/TProtocolException.cs b/lib/csharp/src/Protocol/TProtocolException.cs
index bc002d3..05eb2db 100644
--- a/lib/csharp/src/Protocol/TProtocolException.cs
+++ b/lib/csharp/src/Protocol/TProtocolException.cs
@@ -32,7 +32,8 @@
 		public const int NEGATIVE_SIZE = 2;
 		public const int SIZE_LIMIT = 3;
 		public const int BAD_VERSION = 4;
-		public const int NOT_IMPLEMENTED= 5;
+		public const int NOT_IMPLEMENTED = 5;
+		public const int DEPTH_LIMIT = 6;
 
 		protected int type_ = UNKNOWN;