build: migrate to C++17

Change-Id: Ic5c01274f62556764ea96fc232cf3d835c4ab659
diff --git a/src/detail/bzip2-helper.hpp b/src/detail/bzip2-helper.hpp
index 47ff5ac..9eb966d 100644
--- a/src/detail/bzip2-helper.hpp
+++ b/src/detail/bzip2-helper.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
 /*
- * Copyright (c) 2012-2021 University of California, Los Angeles
+ * Copyright (c) 2012-2022 University of California, Los Angeles
  *
  * This file is part of ChronoSync, synchronization library for distributed realtime
  * applications for NDN.
@@ -22,8 +22,7 @@
 
 #include <ndn-cxx/encoding/buffer.hpp>
 
-namespace chronosync {
-namespace bzip2 {
+namespace chronosync::bzip2 {
 
 /**
  * @brief Compress @p buffer of size @p bufferSize with bzip2
@@ -37,7 +36,6 @@
 std::shared_ptr<ndn::Buffer>
 decompress(const char* buffer, size_t bufferSize);
 
-} // namespace bzip2
-} // namespace chronosync
+} // namespace chronosync::bzip2
 
 #endif // CHRONOSYNC_DETAIL_BZIP2_HELPER_HPP