Use argp in grub-fstest.

	Use argp in grub-fstest.

	* util/grub-fstest.c: Don't include getopt.h.
	Include argp.h.
	(root): New variable.
	(args_count): Likewise.
	(nparm): Likewise.
	(num_disks): Likewise.
	(images): Likewise.
	(cmd): Likewise.
	(debug_str): Likewise.
	(args): Likewise.
	(options): Transformed to argp.
	(usage): Removed.
	(main): Split argument parsing into ...
	(argp_parser): ... this. Changed to argp format.
	(argp): New variable.
	(main): Use argp_parse.