Some filesystems (NFS in particular) do not fill out the d_type field
when returning directory entries through readdir(3). In this case we
need to obtain the file type ourselves; otherwise newsyslog -t will not
be able to find archived log files and will fail to both delete old log
files and to do interval-based rotations properly.
Merge branch '20130511-newsyslog-dirent-unknown-type' into markj-develop