[messages] add INFO_MSG and print it to GCS console

Uses a separate string_of_chars function for now to convert the
char array from ivy (e.g. |i,n,f,o, ,m,s,g|) to normal string to
nicely write to console and messages app.

Proper solution would be to write char arrays as normal "quoted string" to the ivy bus.

sw/lib/ocaml/pprz.ml

@@ -164,6 +164,18 @@ let rec string_of_value = function
   | String s -> s
   | Array a -> "|"^(String.concat separator (Array.to_list (Array.map string_of_value a)))^"|"
 
+let rec string_of_chars = function
+    Int x -> string_of_int x
+  | Float x -> string_of_float x
+  | Int32 x -> Int32.to_string x
+  | Int64 x -> Int64.to_string x
+  | Char c -> String.make 1 c
+  | String s -> s
+  | Array a -> let vl = Array.to_list (Array.map string_of_chars a) in
+               match a.(0) with
+                   Char x -> String.concat "" vl
+                 | _ -> "|"^(String.concat separator vl)^"|"
+
 
 let magic = fun x -> (Obj.magic x:('a,'b,'c) Pervasives.format)
 

sw/lib/ocaml/pprz.mli

@@ -63,6 +63,7 @@ val is_fixed_array_type : string -> bool
 
 val size_of_field : field -> int
 val string_of_value : value -> string
+val string_of_chars : value -> string
 val formatted_string_of_value : 'a -> value -> string
 val int_of_value : value -> int (* May raise Invalid_argument *)
 type type_descr = {