Fix two potential segfaults.
Cosmetics.

resizing which is horrible. Upcomming commit will fix that.

Unused video outputs are currently attached to libvlc, so there is no
point in destroying them from the playlist (twice), then from libvlc.
This should also fix #1593 (multiple vout free).

for in english code)

libvlccore: "intf-show" is now a libvlc var instead of a playlist var. This removes a vout->playlist dependency.

We shouldn't look for the playlist from the vout too... but...

This improves readability a lot and prevent us from reinventing the wheel.

Else there is a circular dependency between the vout that yield() the input, where the vout is also an input child. This should fix properly the media_instance() tests.

This sanitize the circular dependency there is between playlist and input and allow a safe destruction.

Revert some errors in 85943656 and 9630c00c

misc/objects.c: Don't rely on vlc_object_destroy() to destroy objects, but expects vlc_object_release to do it when the refcount goes to zero.
* Meaning, that when created objects gets a refcount to 1.
* Destroying is instantaneous and we don't have to poll for a few secondss or so to wait until the object's refcount reach 0.
* We now track vlc_object_t's mem leaks when libvlc_global is released (Hard error for now, so they don't get unoticed)
* We fail hard if an object is released with a refcount of 1 without being detached from its parent and its children, to make sure such cases don't go unoticed.
(make test or make check still pass after that one. VLC is known to leak one object when no module is loaded, this must be fixed).

Missing some cases that I could not test.
Also ffmpeg/chroma.c is locked, so I can but leave it broken.
Fix is for the remaining modules is obvious and the issue is easy to detect.

Enforce access to input_item_t through input_item_{G,S}et*()
Unlock mutexes before calling these functions
Free strings returned by input_item_Get*()

New functions added:

char * input_item_GetURI( input_item_t  * )
void input_item_SetURI( input_item_t * , char * )

mtime_t input_item_GetDuration( input_item_t * )
void input_item_SetDuration( input_item_t * , mtime_t )

to access input_item_t->psz_uri and input_item_t->i_duration

Fix [21193]