Missing bits of previous changeset. Fixes Libvlc.

Use fixed owner structure instead of deprecated VLC events.

Like SD, and in fact most VLC object types, RD is not meant for objects
shared by multiple threads (input, vout, aout...). Using a custom
release makes no sense here.

Signed-off-by: Thomas Guillem <thomas@gllm.fr>

Bad habit but it's for the sake of coherence.

This new type of module will be used to discover renderers (chromecast, UPnP
Renderer, miracast, airport, DIAL, ConeCast).

These modules will send new vlc_renderer_item via an event manager callback.
This new kind of item contain the necessary information to setup a new sout.
Also-by: Steve Lhomme <robux4@videolabs.io>