Disable const in strict mode.

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index b7e57aa228ea22f7db50da0fabb2aecd8445e5f7..f0efd5c3b21deb8f6390808752ce3b8e81a8f0c2 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -226,6 +226,7 @@ function FormatMessage(message) {
       strict_reserved_word:         ["Use of future reserved word in strict mode"],
       strict_delete:                ["Delete of an unqualified identifier in strict mode."],
       strict_delete_property:       ["Cannot delete property '", "%0", "' of ", "%1"],
+      strict_const:                 ["Use of const in strict mode."],
     };
   }
   var message_type = %MessageGetType(message);