lsdb: emit signals when modified

RoutingTable and NamePrefixTable consume the signal
and behave accordingly.

refs: #4127

Change-Id: I6540f30f0222f804b01dc7d9640831c84e5264cc
diff --git a/src/lsa/coordinate-lsa.hpp b/src/lsa/coordinate-lsa.hpp
index 4b07627..c1d3a13 100644
--- a/src/lsa/coordinate-lsa.hpp
+++ b/src/lsa/coordinate-lsa.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2020,  The University of Memphis,
+ * Copyright (c) 2014-2021,  The University of Memphis,
  *                           Regents of the University of California,
  *                           Arizona Board of Regents.
  *
@@ -98,6 +98,9 @@
   std::string
   toString() const override;
 
+  std::tuple<bool, std::list<ndn::Name>, std::list<ndn::Name>>
+  update(const std::shared_ptr<Lsa>& lsa) override;
+
 private:
   double m_hyperbolicRadius = 0.0;
   std::vector<double> m_hyperbolicAngles;