vlclua_playlist_add_internal() requires the playlist only if there is
no parent item. There is always a parent item when demuxing.

pl_Get() has side effects.

This does not really work anyway.

Sorry...

The thread is not cancelled (ever since vlc_clone() replaced
vlc_thread_create()).

This is simpler and more consistent.

In the original stream_Demux (from 2004), there was a lock. But then
it vanished in a big input "rework"... Anyway, killing the demux
explicitly should not be needed: The underlying stream will return EOF
and any sane demux will return on EOF.

This is for backward compatibility with existing VLC playlists and
VLC playlist generators.

So the code is reusable for radio device nodes.

Signed-off-by: Konstantin Pavlov <thresh@videolan.org>

Pointed-out-by: Aurélien Nephtali <aurelien.nephtali@gmail.com>

Note that versions 1.24 and later of GNU/libidn are dual-licensed under
GPLv2+ and LGPLv3+. As with GnuTLS or Samba client, there are 3 ways
to retain LibVLC binaries under LGPLv2.1+:
 - link against a version of GNU/libidn from last year (or older),
 - do not support IDN at all,
 - use another IDNA back-end (e.g. Windows Vista's Normaliz.dll).

When there is an ambiguity, the caller is responsible for determining
whether a string is an URL or a path. In most cases, the string is
known as a file path.

Recent entries are already MRLs.

Close #7108