(we_are_root): Now bool, not int.

(we_are_root): Now bool, not int.
(check_time): Warn about implausibly old time stamps.
(set_stat): Use utimbuf, not stat_info.
(preprare_to_extract): New arg DIRECTORY.
(fill_in_sparse_array): Moved here from compare.c.
(extract_sparse_file): Now returns off_t, giving size left.
Truncate file at end.
(extract_archive): Use safer_name_suffix rather than rolling our own.
Use fill_in_sparse_array rather than rolling our own.
Strip trailing slashes more effectively.
Check for unsafe names.