(dir_list_grow): new public API of dir_list.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(handle_path): don't check list size here.

(handle_dirent): likewise.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
NOT TESTED: Add dir_list::len member to keep number of items in list.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>