Encapsulate xml serialization in xmlprotocol.mli

This eases the task of replacing/improving the serializer, as well as
making it more resistant. See pitfalls below:

Main changes are:

- fold `message` type into `feedback` type
- make messages of type `Richpp.richpp` so we are explicit about the
  content being a rich document.
- moved serialization functions for messages and stateid to `Xmlprotocol`
- improved a couple of internal API points (`is_message`).

Tested.

1 files changed, 3 insertions, 7 deletions

diff --git a/ide/ide_slave.ml b/ide/ide_slave.ml
index 4b043661e0..0e09d84095 100644
--- a/ide/ide_slave.ml
+++ b/ide/ide_slave.ml
@@ -453,16 +453,12 @@ let print_xml =
 let slave_logger xml_oc level message =
   (* convert the message into XML *)
   let msg = hov 0 message in
-  let message = {
-    Feedback.message_level = level;
-    Feedback.message_content = (Richpp.repr (Richpp.richpp_of_pp msg));
-  } in
-  let () = pr_debug (Printf.sprintf "-> %S" (string_of_ppcmds msg)) in
-  let xml = Feedback.of_message message in
+  let () = pr_debug (Printf.sprintf "-> %S" (string_of_ppcmds msg))    in
+  let xml = Xmlprotocol.of_message level (Richpp.richpp_of_pp message) in
   print_xml xml_oc xml
 
 let slave_feeder xml_oc msg =
-  let xml = Feedback.of_feedback msg in
+  let xml = Xmlprotocol.of_feedback msg in
   print_xml xml_oc xml
 
 (** The main loop *)