openflow_input: add bsn_role_status extension

This is a backport of the OpenFlow 1.4 message.
diff --git a/openflow_input/bsn_role_status b/openflow_input/bsn_role_status
new file mode 100644
index 0000000..f53ff23
--- /dev/null
+++ b/openflow_input/bsn_role_status
@@ -0,0 +1,55 @@
+// Copyright 2013, Big Switch Networks, Inc.
+//
+// LoxiGen is licensed under the Eclipse Public License,
+// version 1.0 (EPL), with the following special exception:
+//
+// LOXI Exception
+//
+// As a special exception to the terms of the EPL, you may
+// distribute libraries generated by LoxiGen (LoxiGen Libraries)
+// under the terms of your choice, provided that copyright and
+// licensing notices generated by LoxiGen are not altered or removed
+// from the LoxiGen Libraries and the notice provided below is (i)
+// included in the LoxiGen Libraries, if distributed in source code
+// form and (ii) included in any documentation for the LoxiGen
+// Libraries, if distributed in binary form.
+//
+// Notice: "Copyright 2013, Big Switch Networks, Inc.
+// This library was generated by the LoxiGen Compiler."
+//
+// You may not use this file except in compliance with the EPL or
+// LOXI Exception. You may obtain a copy of the EPL at:
+//
+// http://www.eclipse.org/legal/epl-v10.html
+//
+// 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 EPL for the specific language
+// governing permissions and limitations under the EPL.
+
+// Backport the OpenFlow 1.4 role status message
+//
+// This message will be sent when a controller's role changes for any reason
+// other than it using OFPT_ROLE_REQUEST.
+
+#version 4
+
+enum ofp_bsn_controller_role_reason(wire_type=uint8_t) {
+    OFP_BSN_CONTROLLER_ROLE_REASON_MASTER_REQUEST = 0,
+    OFP_BSN_CONTROLLER_ROLE_REASON_CONFIG = 1,
+    OFP_BSN_CONTROLLER_ROLE_REASON_EXPERIMENTER = 2,
+};
+
+struct of_bsn_role_status : of_bsn_header {
+    uint8_t version;
+    uint8_t type == 4;
+    uint16_t length;
+    uint32_t xid;
+    uint32_t experimenter == 0x5c16c7;
+    uint32_t subtype == 55;
+    enum ofp_controller_role role;
+    enum ofp_bsn_controller_role_reason reason;
+    pad(3);
+    uint64_t generation_id;
+};