Refactor and modernize namespace declarations

Move all unit tests to namespace nfd::tests

Delete unused header core/algorithm.hpp

Change-Id: I5591f0c5f3bb5db67f8b45fae95471f8a555ca68
diff --git a/daemon/rib/fib-update.hpp b/daemon/rib/fib-update.hpp
index 5339a37..6eead74 100644
--- a/daemon/rib/fib-update.hpp
+++ b/daemon/rib/fib-update.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2019,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -28,8 +28,7 @@
 
 #include "core/common.hpp"
 
-namespace nfd {
-namespace rib {
+namespace nfd::rib {
 
 /** \class FibUpdate
  *  \brief represents a FIB update
@@ -90,7 +89,6 @@
   return os;
 }
 
-} // namespace rib
-} // namespace nfd
+} // namespace nfd::rib
 
 #endif // NFD_DAEMON_RIB_FIB_UPDATE_HPP