include/starpu_perfmodel.h: define a invalid value for perfmodel type

include/starpu_perfmodel.h

@@ -1,7 +1,7 @@
 /* StarPU --- Runtime system for heterogeneous multicore architectures.
  *
  * Copyright (C) 2010-2014  Université de Bordeaux 1
- * Copyright (C) 2010, 2011, 2012, 2013  Centre National de la Recherche Scientifique
+ * Copyright (C) 2010, 2011, 2012, 2013, 2014  Centre National de la Recherche Scientifique
  * Copyright (C) 2011  Télécom-SudParis
  *
  * StarPU is free software; you can redistribute it and/or modify
@@ -107,6 +107,7 @@ struct starpu_perfmodel_per_arch
 
 enum starpu_perfmodel_type
 {
+        STARPU_PERFMODEL_INVALID=0,
 	STARPU_PER_ARCH,
 	STARPU_COMMON,
 	STARPU_HISTORY_BASED,