fix issues related to export & function (#2002)

- `unused` function names
- confusion with function call syntax

fixes #2001

lib/transform.js

@@ -240,6 +240,7 @@ TreeTransformer.prototype = new TreeWalker;
     });
 
     _(AST_Export, function(self, tw){
+        if (self.exported_definition) self.exported_definition = self.exported_definition.transform(tw);
         if (self.exported_value) self.exported_value = self.exported_value.transform(tw);
     });