Strip out some code to support Boost <1.70

The minimum version that works is 1.70, so this code is no longer
useful.

include/spead2/common_socket.h

@@ -51,25 +51,6 @@ void set_socket_send_buffer_size(SocketType &socket, std::size_t buffer_size);
 template<typename SocketType>
 void set_socket_recv_buffer_size(SocketType &socket, std::size_t buffer_size);
 
-#if BOOST_VERSION >= 107000
-/**
- * Get an object suitable for constructing another socket with the same IO
- * context. The return type depends on the Boost version. This is necessary
- * because Boost 1.70 removed @c basic_socket::get_io_context.
- */
-template<typename SocketType>
-static inline typename SocketType::executor_type get_socket_executor(SocketType &socket)
-{
-    return socket.get_executor();
-}
-#else
-template<typename SocketType>
-static inline boost::asio::io_context &get_socket_executor(SocketType &socket)
-{
-    return socket.get_io_context();
-}
-#endif
-
 /**
  * Determine whether a socket is using a particular IO context. This is necessary
  * because Boost 1.70 removed @c basic_socket::get_io_context.
@@ -82,10 +63,8 @@ static inline bool socket_uses_io_context(SocketType &socket, boost::asio::io_co
     typedef boost::asio::io_context::executor_type executor_type;
     return socket.get_executor().target_type() == typeid(executor_type)
           && *socket.get_executor().template target<executor_type>() == io_context.get_executor();
-#elif BOOST_VERSION >= 107000
-    return socket.get_executor() == io_context.get_executor();
 #else
-    return &socket.get_io_context() == &io_context;
+    return socket.get_executor() == io_context.get_executor();
 #endif
 }
 

src/recv_tcp.cpp

@@ -49,7 +49,7 @@ tcp_reader::tcp_reader(
     buffer(new std::uint8_t[max_size * pkts_per_buffer]),
     head(buffer.get()),
     tail(buffer.get()),
-    peer(get_socket_executor(acceptor)),
+    peer(acceptor.get_executor()),
     acceptor(std::move(acceptor))
 {
     assert(socket_uses_io_context(this->acceptor, get_io_context()));