This is useful at the maximum depth level, to update newly created
directories. It is however questionable if the hard-coded 5 seconds
delay is enough to create new directory trees with all of their files,
but we might make that delay configurable in the future.
This patch implements a light-weight inotify library, and watches all
directories below the music directory. It updates all directories
where files changed after a delay of 5 seconds.
