libvlc: rename libvlc_media_descriptor to libvlc_media and libvlc_media_instance to libvlc_media_player.

Wrong dir

This reverts commit f11a132c.

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

This reverts commit 1dfd50c2.
This is no needed of such a hack if there is no circular dependency between input and vout and if the input are properly released.

Else there is a circular dependency between the vout that yield() the input, where the vout is also an input child. This should fix properly the media_instance() tests.

stream: No use to vlc_object_yield() and object that create ourslef, and that a race could possibly corrupt in case of bad usage.

stats: Move the stat to libvlc instead of the playlist. As stated in the code it is not playlist related.