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

Patch: Jens Geyer
diff --git a/lib/ocaml/src/Thrift.ml b/lib/ocaml/src/Thrift.ml
index f176a43..f0d7a42 100644
--- a/lib/ocaml/src/Thrift.ml
+++ b/lib/ocaml/src/Thrift.ml
@@ -261,6 +261,8 @@
       | NEGATIVE_SIZE
       | SIZE_LIMIT
       | BAD_VERSION
+      | NOT_IMPLEMENTED
+      | DEPTH_LIMIT
 
   exception E of exn_type * string;;