Enforce naming conventions and allow empty (except for the header) types.hal files.
diff --git a/Interface.cpp b/Interface.cpp
index 054a869..ef4b573 100644
--- a/Interface.cpp
+++ b/Interface.cpp
@@ -42,5 +42,9 @@
     out << "};\n\n";
 }
 
+bool Interface::isInterface() const {
+    return true;
+}
+
 }  // namespace android