* common/dotlock.h (DOTLOCK_LOCK_BY_PARENT, DOTLOCK_LOCKED): New.
* common/dotlock.c [HAVE_POSIX_SYSTEM]: Include <dirent.h>.
(dotlock_get_process_id, dotlock_detect_tname): New.
(dotlock_create_unix): Handle the case when no_write option is
specified.  Not creating the lock file, but detect the the file of
tname.
(dotlock_create) [HAVE_POSIX_SYSTEM]: Add support of
DOTLOCK_LOCK_BY_PARENT and DOTLOCK_LOCKED for dotlock CLI util.
(dotlock_take_unix): Support the case of DOTLOCK_LOCK_BY_PARENT.