/usr/include/boost/locale/ is in libboost1.62-dev 1.62.0+dfsg-5.
This file is owned by root:root, with mode 0o755.
..
/usr/include/boost/locale/boundary/
/usr/include/boost/locale/boundary.hpp
/usr/include/boost/locale/boundary/boundary_point.hpp
/usr/include/boost/locale/boundary/facets.hpp
/usr/include/boost/locale/boundary/index.hpp
/usr/include/boost/locale/boundary/segment.hpp
/usr/include/boost/locale/boundary/types.hpp
/usr/include/boost/locale/collator.hpp
/usr/include/boost/locale/config.hpp
/usr/include/boost/locale/conversion.hpp
/usr/include/boost/locale/date_time.hpp
/usr/include/boost/locale/date_time_facet.hpp
/usr/include/boost/locale/definitions.hpp
/usr/include/boost/locale/encoding.hpp
/usr/include/boost/locale/encoding_errors.hpp
/usr/include/boost/locale/encoding_utf.hpp
/usr/include/boost/locale/format.hpp
/usr/include/boost/locale/formatting.hpp
/usr/include/boost/locale/generator.hpp
/usr/include/boost/locale/generic_codecvt.hpp
/usr/include/boost/locale/gnu_gettext.hpp
/usr/include/boost/locale/hold_ptr.hpp
/usr/include/boost/locale/info.hpp
/usr/include/boost/locale/localization_backend.hpp
/usr/include/boost/locale/message.hpp
/usr/include/boost/locale/time_zone.hpp
/usr/include/boost/locale/utf.hpp
/usr/include/boost/locale/utf8_codecvt.hpp
/usr/include/boost/locale/util.hpp