include/starpu_perfmodel.h: add comment stating that type is deprecated (do not know how to do it with attribute __deprecated__

include/starpu_perfmodel.h

@@ -141,6 +141,7 @@ struct starpu_perfmodel_regression_model
 
 struct starpu_perfmodel_history_table;
 
+/* using starpu_per_arch_perfmodel is deprecated */
 #define starpu_per_arch_perfmodel starpu_perfmodel_per_arch
 
 struct starpu_perfmodel_per_arch