lp: add PrefixAnnouncement field and tag

refs #4280

Change-Id: I05b1f300d188388d60b3ed364f04d03de3fefccb
diff --git a/src/lp/tlv.hpp b/src/lp/tlv.hpp
index fb24ab3..1b409ca 100644
--- a/src/lp/tlv.hpp
+++ b/src/lp/tlv.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -45,6 +45,7 @@
   Ack = 836,
   TxSequence = 840,
   NonDiscovery = 844,
+  PrefixAnnouncement = 848,
 };
 
 enum {