Fix memleak. Return E_GENERIC instead of displaying an error message.
Signed-off-by: Laurent Aimar <fenrir@videolan.org>

Signed-off-by: Laurent Aimar <fenrir@videolan.org>

Signed-off-by: Laurent Aimar <fenrir@videolan.org>

 - XML encode everything (especially URL), not just some parameters,
 - use fputs() as appropriate,
 - remove a shadowed variable,
 - print duration as a 64-bits quantity.

I want to use function pointers in a later commit...

The Audio class can only be created/destroyed by the associated MediaPlayer
class. I will add some copy constructor later on.

- 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)