* lib/long-options.c (parse_long_options): Use EXIT_SUCCESS instead
of 0.
(parse_gnu_standard_options_only): Add function to
process the GNU default options --help and --version and fail for any other
unknown long or short option. See
https://gnu.org/prep/standards/html_node/Command_002dLine-Interfaces.html .
* lib/long-options.h (parse_gnu_standard_options_only): Declare it.
* modules/long-options (depends-on): Add stdbool, exitfail.
* top/maint.mk (sc_prohibit_long_options_without_use): Update
syntax-check rule, add new function name.