- Playlist items are stored only once. No category / onelevel separation
- Services Discovery nodes always stay a tree
- The playlist and Media Library are tree or flat depending on variable "playlist-tree".
  It means that if the setting variable says flat, the items that come from playlist
  demuxers are flattened into a single level list.
- The design demanded a different playlist demuxing system. Now playlist demuxers should
  construct a tree of items under an input_item_node_t root and send that using
  input_item_AddSubItemTree. Currently, the old scheme will be retained in modules, because
  there is still some listening to the old event in code (the libvlc media system for example)

Signed-off-by: Pierre d'Herbemont <pdherbemont@free.fr>

That was meant for DCCP and UDP-Lite but it shouldn't be needed.

 - enable (non-ES) settings even if no output is present
 - best effort at handling multiple outputs
 - remove exceptions
 - libvlc_video_get_size returns both dimensions
 - libvlc_video_take_snapshot takes a parameter to select the output

TBD: Makefile

Fix regression brought by ce67728a
As stated in the 'BIG FAT WARNING', decoder_t and filter_t first members must
be the same ones.

This solves skins2 numerous images failing to be displayed due to swscale
 video filter no longer working properly (a filter_t to decoder_t cast issue)

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>