/usr/include/libtorrent/aux_/ is in libtorrent-rasterbar-dev 1.1.1-1+b1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libtorrent/aux_/alert_manager_variadic_emplace.hpp
/usr/include/libtorrent/aux_/allocating_handler.hpp
/usr/include/libtorrent/aux_/byteswap.hpp
/usr/include/libtorrent/aux_/cpuid.hpp
/usr/include/libtorrent/aux_/disable_warnings_pop.hpp
/usr/include/libtorrent/aux_/disable_warnings_push.hpp
/usr/include/libtorrent/aux_/escape_string.hpp
/usr/include/libtorrent/aux_/file_progress.hpp
/usr/include/libtorrent/aux_/merkle.hpp
/usr/include/libtorrent/aux_/openssl.hpp
/usr/include/libtorrent/aux_/proxy_settings.hpp
/usr/include/libtorrent/aux_/session_call.hpp
/usr/include/libtorrent/aux_/session_impl.hpp
/usr/include/libtorrent/aux_/session_interface.hpp
/usr/include/libtorrent/aux_/session_settings.hpp
/usr/include/libtorrent/aux_/time.hpp