(cherry picked from commit 105335dd)

When i_size is sufficiently large, we would overflow malloc(), and then
overwrite the heap with stream_Read().

Bug reported by: Alin Rad Pop, Secunia Research.

(cherry-picked from commit 95e2f0ff579a5b987cbde9454aa1fc86080528e2)

(for example, on invalid file ...)

   share/lua/meta/googleimage.lua, function fetch_art(): share/lua/meta/googleimage.lua:43: calling
   'stream' on bad self (string expected, got table)

...so we don't try to vout_Control() it after it's been destroyed.
We cannot yield the video output for real either, as it would prevent
it from being destroyed once it is not needed anymore.

Releasing other thread's references is not a very good idea...

The error message was overriden to "Illegal seek"

Should fix assertion errors.

Signed-off-by: Rémi Denis-Courmont <rdenis@simphalempin.com>