gpgtar,w32: Support file names longer than MAX_PATH.
* tools/gpgtar.c: Replace assert by log_assert. * tools/gpgtar-extract.c: Ditto. (extract_regular): Create files with sysopen flag. * tools/gpgtar-create.c (scan_directory): Use gpgrt_fname_to_wchar.
Note that for this change libgpg-error 1.45 is required for Windows.