Strip Interface class of most of its logic, make it all about Module exports

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index b554175bccf21b27e295adb7517c192566a0a01e..19d61041d1942c400b9fce07e56ca39a2130d38a 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -175,7 +175,6 @@ var kMessages = {
   symbol_to_primitive:           ["Cannot convert a Symbol wrapper object to a primitive value"],
   symbol_to_number:              ["Cannot convert a Symbol value to a number"],
   invalid_module_path:           ["Module does not export '", "%0", "', or export is not itself a module"],
-  module_type_error:             ["Module '", "%0", "' used improperly"],
   module_export_undefined:       ["Export '", "%0", "' is not defined in module"],
   unexpected_super:              ["'super' keyword unexpected here"],
   extends_value_not_a_function:  ["Class extends value ", "%0", " is not a function or null"],