readelf: cmdline data

readelf: cmdline data

Don't use a struct filedata for cmdline, which only needs two of the
filedata fields.

	* readelf.c (struct dump_data): New, used..
	(cmdline): ..here, and..
	(struct filedata): ..here.  Adjust all uses.
	(request_dump_bynumber, request_dump, parse_args): Pass in a
	struct dump_data* rather than Filedata*.  Adjust callers.
	(main): Don't set cmdline.file_name.