Missed bit of previous commit.

From-SVN: r216221

gcc/c-family/c-cppbuiltin.c

@@ -891,6 +891,7 @@ c_cpp_builtins (cpp_reader *pfile)
   builtin_define_type_max ("__PTRDIFF_MAX__", ptrdiff_type_node);
   builtin_define_type_max ("__SIZE_MAX__", size_type_node);
 
+  if (c_dialect_cxx ())
     for (i = 0; i < NUM_INT_N_ENTS; i ++)
       if (int_n_enabled_p[i])
 	{