interim checkin of the rebased code

src/cryptonote_core/blockchain.h

@@ -29,7 +29,8 @@
 // Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
 
 #pragma once
-#include <boost/asio/io_service.hpp>
+#include <boost/asio/executor_work_guard.hpp>
+#include <boost/asio/io_context.hpp>
 #include <boost/function/function_fwd.hpp>
 #if BOOST_VERSION >= 107400
 #include <boost/serialization/library_version_type.hpp>
@@ -1280,9 +1281,9 @@ namespace cryptonote
     crypto::hash m_difficulty_for_next_block_top_hash;
     difficulty_type m_difficulty_for_next_block;
 
-    boost::asio::io_service m_async_service;
+    boost::asio::io_context m_async_service;
     boost::thread_group m_async_pool;
-    std::unique_ptr<boost::asio::io_service::work> m_async_work_idle;
+    std::unique_ptr<boost::asio::executor_work_guard<boost::asio::io_context::executor_type>> m_async_work_idle;
 
     // some invalid blocks
     blocks_ext_by_hash m_invalid_blocks;     // crypto::hash -> block_extended_info