XSPF: support element duration
To reproduce:
- Start VLC
- Empty your playlist
- Add some images to your playlist
- Save as XSPF
- Edit the timeout from 10000 to 3500 with your favorite text editor
- Close VLC
- Open VLC again
- Open the XSPF playlist and click the first item to play
What happens: The slideshow starts using a timeout of 10000 milliseconds.
Expected: The slideshow starts using a timeout of 3500 milliseconds, as mandated by the XSPF playlist file.