Ensure that the standard library is loaded first. This fixes the bug...

Ensure that the standard library is loaded first. This fixes the bug introduced by my incorrect refactoring in commit 6abe2316.

src/front.ml

@@ -62,10 +62,14 @@ let grammars : Syntax.partial_grammar list =
        [Settings.stdlib_filename]. This file name can appear in generated
        parsers, because Menhir produces # directives that point back to
        source (.mly) files. *)
-    load_grammar_from_contents
-      Settings.stdlib_filename
-      Standard_mly.contents ::
-    grammars()
+    (* Note that the [let] construct below is required in order to ensure
+       that the standard library is read first. *)
+    let standard_library =
+      load_grammar_from_contents
+        Settings.stdlib_filename
+        Standard_mly.contents
+    in
+    standard_library :: grammars()
 
 let () =
   Time.tick "Lexing and parsing"