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

src/rewriter.cc

Index: src/rewriter.cc
diff --git a/src/rewriter.cc b/src/rewriter.cc
index 66961278a76f0161e5152b7f5ce10aea7efc22b5..c81950e8ed6b2f597a0bc4a2b0ad265962c7c48b 100644
--- a/src/rewriter.cc
+++ b/src/rewriter.cc
@@ -206,7 +206,6 @@ void Processor::VisitModuleDeclaration(ModuleDeclaration* node) {}
 void Processor::VisitImportDeclaration(ImportDeclaration* node) {}
 void Processor::VisitExportDeclaration(ExportDeclaration* node) {}
 void Processor::VisitModuleLiteral(ModuleLiteral* node) {}
-void Processor::VisitModuleVariable(ModuleVariable* node) {}
 void Processor::VisitModulePath(ModulePath* node) {}
 void Processor::VisitModuleUrl(ModuleUrl* node) {}
 void Processor::VisitEmptyStatement(EmptyStatement* node) {}