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

Patch: Jens Geyer
diff --git a/lib/delphi/src/Thrift.Protocol.pas b/lib/delphi/src/Thrift.Protocol.pas
index 7ae8e34..4d92cb1 100644
--- a/lib/delphi/src/Thrift.Protocol.pas
+++ b/lib/delphi/src/Thrift.Protocol.pas
@@ -72,13 +72,14 @@
 

   TProtocolException = class( Exception )

   public

-    const

+    const // TODO(jensg): change into enum

       UNKNOWN : Integer = 0;

       INVALID_DATA : Integer = 1;

       NEGATIVE_SIZE : Integer = 2;

       SIZE_LIMIT : Integer = 3;

       BAD_VERSION : Integer = 4;

       NOT_IMPLEMENTED : Integer = 5;

+      DEPTH_LIMIT : Integer = 6;

   protected

     FType : Integer;

   public