playlist: Recurse on ITEM_TYPE_NODE when calculating the duration

When adding an item X whose underlying input_item_t's i_type is
ITEM_TYPE_NODE (like a folder), we need to call playlist_GetNodeDuration
on X again for the duration of X to be the sum of the durations of X's
children.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
Enable JPEG RTP packetization

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>