Improve non-handling by interfaces without interaction

Dirty currently ... 

* Handle interfaces not providing interaction correctly
* Add a new helper to request authentication
* Add return codes

directx.c: fixed the initial grey flicker when using overlay surfaces by postponing painting the overlay colorkey until the first picture has been received the vout display

 using vlc_object_id instead of a direct p_object pointer as parameter
 for mediacontrol_new_from_object

* modules/demux/real.c: improved cook support. We now try to send audio subpackets as soon as they are available instead of waiting for the full re-ordering to be finished. Added some sanity checks as well and gave a try to 28_8 support (not tested).

* modules/demux/real.c: re-order cook subpackets and send them 1 at a time to the decoder. This is required by the new ffmpeg cook codec (It also breaks our binary realaudio codec but I'll repair that later on).