first search  the root of  the object  using p_parent and  not directly
 using p_vlc. If this first search  failed then we search using p_vlc if
 it wasn't the  case. (I'm not sure  it's harmless but I  think it's the
 correct behavour for FIND_ANYWHERE)

 * src/video_output/video_output.c  : we could now  use FIND_ANYWHERE to
 catch the  playlist (even when the  vlc is exiting. (Hehe, now visual
 effects won't reopen the vout every playlist item.)