* argparse.h (ARGPARSE_SHORTOPT_HELP, ARGPARSE_SHORTOPT_VERSION,
ARGPARSE_SHORTOPT_WARRANTY, ARGPARSE_SHORTOPT_DUMP_OPTIONS): New
macros.
(ARGPARSE_end): Add some placeholders for standard options.
* argparse.c (arg_parse): Fill in missing standard options so
default machinery works.  Check for standard options in new way.
Do not write out standard options for --dump-options.