Previously, we only removed links from children to dead parents.
This patch is semantically the same as Funman's earlier
vlc_object_detach_unlocked() patch. It is merely faster and less clean.

Unfortunately, this means it is impossible to detect leaked children.
That being noted, leaving dead parents "semi-attached" in objects tree
is not thread-safe anyhow. Basically, we either automatically detach
objects (and miss leaks), or require children to be detached/destroyed
before their parent is destroyed (and get leaks detection, but more
coding pain).

Signed-off-by: Jean-Paul Saman <jpsaman@videolan.org>

They can only be read safely under the Big Structure Lock in
src/misc/objects.c, so it makes no sense for them to be public.

By the way, making i_children volatile wouldn't magically solve
thread-safety issues. The only correct use of volatile is in dealing
with asynchronous changes _within_ the same thread, such as signal
handling.

P.S.: I wish modules were not objects, and I wonder why they are
(they don't don't use threads, nor plugins, nor variables)

This reverts commit c85f8681.

This reverts commit e5b3d194.

This reverts commit 68bcb6a4.

As pointed by courmisch, this is crashy.

Conflicts:

	src/vlc.c

Note: I don't think we did yet match the old behaviour, if we hit ctrl-c while in libvlc_new(), vlc isn't killed properly.