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 e60ab92586e0a5f4aa2002397492d1d171769e2a..1e0f7a5e25c2ca685bc2a7f359b243be0431380f 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -171,7 +171,6 @@ 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"],