Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

No caller needs this.  Fixes use-after-free after returning from
Client::OnTimeout().

Random access is not necessary here.

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

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.