Allow struct, union and enum type declarations to be annotated.

Change-Id: Idce594b47c324d8420638e2e8853da3c99150672
Bug: 31800672
Test: hidl_test, hidl_test_java
diff --git a/AST.h b/AST.h
index 2d64972..4f1d373 100644
--- a/AST.h
+++ b/AST.h
@@ -48,6 +48,7 @@
     // package and version really.
     FQName package() const;
     bool isInterface(std::string *ifaceName) const;
+    bool containsInterfaces() const;
 
     void enterScope(Scope *container);
     void leaveScope();