(Deprecated: Use native_handle().) Get the native acceptor representation.
This function may be used to obtain the underlying representation of the
acceptor. This is intended to allow access to native acceptor functionality
that is not otherwise provided.
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)