composition: Remove now useless pad probes
composition: Remove now useless external_gst_bin_add_remove field
composition: Empty current_bin on gnl_composition_reset
gnlobject: Allow commiting of object that are not inside a composition
tests: Minor cleanup
composition: Set the state of the internal bin before removing its children

Otherwize when we set the composition state to READY or NULL we can end
up with children in PAUSED state outside of everything
composition: Rename commit_pipeline_func to commit_func

We do not commit any pipeline, we commit the new state of the composition internals
composition: The ref the user gave us is our, and we give another to the bin when needed
composition: Teach the composition to seek same stack
Fix complex
composition: Fix toplevel seek event refcounting
composition: Set *all* children state when going back to READY and then NULL
composition: Actiually set current_bin state even when not debugging
compositition: Check last stack in the children thread

Avoiding to take the OBJECT_LOCK when recieving EOS. The computation is
based on the GstEvent.seqnum to make sure that the EOS we receive
corresponds to the right sequence.

In that patch we tweak seqnums so that they are correctly computed
avoiding to depend on all elements to do it properly as it might pretty
much not be the case!
composition: Force setting children state to NULL rebfore unrefing them
composition: Remove useless flush_start argument from the stop_task method
composition: Add/Remove children in the same order as they were called
Rework the seqnum logic to avoid races when setting the new stack seqnum

When we were seeking the same stack without a logic that gurantees that we actually
saw the seek with the new seqnum set, we could have ended up with an EOS set with
the right seqnum even if it was actually not the case.
composition: Remove useless toplevel_seek argiment from activate_new_stack
composition: Clear the old stack when removing children that where used