improve error message in refcounting plugin

Change-Id: I02b483c1d696913b33112b9248747f9c3d28dc55

compilerplugins/clang/refcounting.cxx

@@ -340,7 +340,8 @@ void RefCounting::checkUnoReference(QualType qt, const Decl* decl, const std::st
                 DiagnosticsEngine::Warning,
                 "uno::Reference " + rDeclName + " with template parameter that does not contain ::static_type() "
                 + qt.getAsString()
-                + ", parent is " + rParentName,
+                + ", parent is " + rParentName
+                + ", should probably be using rtl::Reference instead"
                 decl->getLocation())
               << decl->getSourceRange();
         }