Code cleanup of kqueue.c

Code cleanup of kqueue.c

* src/kqueue.c (kqueue_directory_listing): Skip "." and "..".
(kqueue_compare_dir_list): Do not loop when calling
directory_files_internal.  Remove checks for "." and "..", this is
done in kqueue_directory_listing now.
(Fkqueue_add_watch): Check for proper emacs_open flags.