Add -Wextra-semi -Wundefined-func-template to the default CXXFLAGS

And fix the resulting compilation errors.

Change-Id: I16f679836a0cf2a3ff5dfcf6f6b67bfbfe4cdbd7
Refs: #4248
diff --git a/src/mgmt/nfd/fib-entry.hpp b/src/mgmt/nfd/fib-entry.hpp
index fa609ef..d91f651 100644
--- a/src/mgmt/nfd/fib-entry.hpp
+++ b/src/mgmt/nfd/fib-entry.hpp
@@ -1,5 +1,5 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
+/*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
@@ -84,6 +84,8 @@
   mutable Block m_wire;
 };
 
+NDN_CXX_DECLARE_WIRE_ENCODE_INSTANTIATIONS(NextHopRecord);
+
 bool
 operator==(const NextHopRecord& a, const NextHopRecord& b);
 
@@ -165,6 +167,8 @@
   mutable Block m_wire;
 };
 
+NDN_CXX_DECLARE_WIRE_ENCODE_INSTANTIATIONS(FibEntry);
+
 bool
 operator==(const FibEntry& a, const FibEntry& b);