adde flowlet_switching exercise

SIGCOMM_2015/flowlet_switching/p4src/includes/intrinsic.p4

@@ -0,0 +1,26 @@
+/*
+Copyright 2013-present Barefoot Networks, Inc. 
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+header_type intrinsic_metadata_t {
+    fields {
+        ingress_global_timestamp : 48;
+        lf_field_list : 32;
+        mcast_grp : 16;
+        egress_rid : 16;
+    }
+}
+
+metadata intrinsic_metadata_t intrinsic_metadata;