Enable the local keywords even when the local extension is off (#18)

Author: lpw25

parsing/lexer.mll

@@ -103,9 +103,6 @@ let keyword_table =
 
 let lookup_keyword name =
   match Hashtbl.find keyword_table name with
-  | LOCAL | NONLOCAL | GLOBAL
-       when not (Clflags.Extension.is_enabled Local) ->
-     LIDENT name
   | kw -> kw
   | exception Not_found ->
      LIDENT name

testsuite/tests/typing-local/nosyntax.ml

@@ -7,11 +7,11 @@ type lfn' = local_ string -> int
 [%%expect{|
 type fn = string -> int
 type lfn = (string [@ocaml.local]) -> int
-Line 3, characters 12-25:
+Line 3, characters 19-25:
 3 | type lfn' = local_ string -> int
-                ^^^^^^^^^^^^^
-Error: The type constructor string expects 0 argument(s),
-       but is here applied to 1 argument(s)
+                       ^^^^^^
+Error: The local extension is disabled
+       To enable it, pass the '-extension local' flag
 |}]
 
 let cast (x : fn) = (x : lfn)