The surface mutex is no longer needed now that VASubpictures remember
to which VASurfaceID they were attached. The subpictures are now remembered
inside picture_sys_t directly iso at the vlc_va_surface_t structure.

Release subpicture association when picture is released. Note that picture_pool_New() overrides this
pictures pf_release() function and restores it before cleaning up the picture pool.

When surfaces are reclaimed or released before they are being displayed,
then the subpicture association still exists. This code tries to catch
such pictures and will release the subpictures association.

- do picture refcounting from pf_release() functions.

- Renamed PictureReleaseLocked to ReleaseSurfaceLocked
- Cleanup code paths

Introduce VLC_CODEC_VAAPI_SURFACE to determine what to do with the
passed picture. If VLC_CODEC_VAAPI_SURFACE, then the picture caries
a VASurface which must be used to display. Else it is a normal
picture and should be treated as such.

The video output could also get picture_t * that were not decoded
on the GPU. Still use the GPU to display them.

Center position of subpictures which looks better.

Conflicts:
	modules/codec/avcodec/Modules.am
	src/video_output/vout_subpictures.c

Close #4798

 * Remove legacy methods
 * Implement the GoTo method

Thanks to j-b and ivoire

really route messages to tracklist interface
fix DBUS_MPRIS_TRACKLIST_INTERFACE definition
fix CanQuit/CanRaise/HasTracklist input types

fix AddTrack function
The function has changed in mpris 2.1, but the additional parameter isn't being used by VLC (yet)

loop/repeat controls are gone, we now need a tri-state button
track change signal doesn't exist anymore in mpris 2.1 and i can't find how
we can be notified of track changes

thanks to mirsal

- exchange U and V plane to get the right colors again
- fixed some compiler warnings about signed - unsigned compare
- and some missing case entries

It also removes useless thread wake up.

Fix #4797

Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>