OCaml 4.02 compat

Author: jonludlam

src/odoc/extract_code.cppo.ml

@@ -239,6 +239,6 @@ let extract ~dst ~input ~names ~line_directives ~warnings_options =
 #else
 
 let extract ~dst:_ ~input:_ ~names:_ ~line_directives:_ ~warnings_options:_ =
-  Error (`Msg "Extract-code is not available for OCaml < 4.10")
+  Result.Error (`Msg "Extract-code is not available for OCaml < 4.10")
 
 #endif

src/odoc/extract_code.mli

@@ -4,4 +4,4 @@ val extract :
   names:string list ->
   line_directives:bool ->
   warnings_options:Odoc_model.Error.warnings_options ->
-  (unit, [> `Msg of string ]) result
+  (unit, [> `Msg of string ]) Result.result