composition: Implement a separate probe to drop data.

It ensures that all data that still flows while we update the
pipeline is dropped, otherwise we have races where we could get
buffer from the old pipeline flowing into elements that are already
fully flushed (and have no segment caps, etc... set)

Also validate the stack a little later.

This commits finnishes what had been started with
a24a3be13b81c5d0080c061edf61daece6341f95
composition: Validate stack right after it has been re computed
composition: Release objects lock while forwarding an event

There is no reason to keep it and in some rare cases it creates
deadlocks as followed:
  t1:
     → Composition receives a flushing seek, it takes the OBJECTS_LOCK
        and fowards the flushing seek event upstream
     → adder receives the seek and set its collectpad to flushing
        This implies tacking STREAM_LOCK (collectpad)

  t2:
    → Collectpad has buffers ready, and has the STREAM_LOCK
    (collectpad) and is EOS, so it sends it downstream
    → The composition receives EOS, and needs to check if it is
    the actual EOS or not, thus need to take the OBJECTS_LOCK

This create a deadlock, and in the first stage, we did not need the
OBJECTS_LOCK to forward downstream the flushing seek, so do not take
it.

https://bugzilla.gnome.org/show_bug.cgi?id=706831
composition: Do not update the pipeline if we are in NULL state

And always update start/duration when removing an object from the
composition
Automatic update of common submodule

From 01a7a46 to 74a6857
Automatic update of common submodule

From 74a6857 to b613661
Automatic update of common submodule

From b613661 to 6b03ba7
Automatic update of common submodule

From 6b03ba7 to 865aa20
Release 1.1.90
Back to development
Automatic update of common submodule

From 865aa20 to dbedaa0
gnlcomposition: Fix typo
Automatic update of common submodule

From dbedaa0 to d48bed3
gnloperation: Remove dead code

ret is only set before leaving the loop.

COVERITY CID 1139661
COVERITY CID 1139662
Automatic update of common submodule

From d48bed3 to 1a07da9
Automatic update of common submodule

From 1a07da9 to fe1672e
Automatic update of common submodule

From fe1672e to bcb1518
Release 1.2.0
Back to development
tests: pass 64-bit integers to 64-bit integer properties