Use UTF-8 file API if supported by HDF5 library. * m4/acinclude.m4 (OCTAVE_CHECK_HDF5_HAS_UTF8_API): Add test to check if HDF5 library uses UTF-8 file API on Windows (version 1.12 or newer). * configure.ac (HDF5): Run new configure test. * libinterp/corefcn/ls-hdf5.cc (hdf5_fstreambase::open_create), libinterp/corefcn/load-save.cc (load_save_system::get_file_format, load_save_system::save): The kludge that was used to work with non-ASCII characters in HDF5 file names can be removed if the used version of HDF5 supports UTF-8 encoded file names.