actor: Use proper internal API
actor: Use proper internal API

Inside the set_child_[above|below]_sibling() and set_child_at_index() we
should be using the internal API for mutating the children list, instead
of the delegate functions. This ensures that we go through a single,
well-defined code path for all operations on the list of children of
an actor.

ebassi/clutter,GNOME/clutter,Distrotech/clutter,djdeath/clutter-multithreaded,collects/clutter,Distrotech/clutter,djdeath/clutter-android,GNOME/clutter,djdeath/clutter,djdeath/clutter,djdeath/clutter-multithreaded,heysion/clutter-clone,heysion/clutter-clone,djdeath/clutter,jigpu/clutter,jigpu/clutter,GNOME/clutter,djdeath/clutter-multithreaded,collects/clutter,ebassi/clutter,jigpu/clutter,djdeath/clutter-android,ebassi/clutter,Distrotech/clutter,GNOME/clutter,heysion/clutter-clone,ebassi/clutter,djdeath/clutter-multithreaded,kerrickstaley/clutter-vala,Distrotech/clutter,collects/clutter,Distrotech/clutter,djdeath/clutter-android,djdeath/clutter-android,Distrotech/clutter,kerrickstaley/clutter-vala,djdeath/clutter,jigpu/clutter,heysion/clutter-clone,kerrickstaley/clutter-vala,GNOME/clutter,djdeath/clutter,djdeath/clutter,jigpu/clutter,jigpu/clutter,kerrickstaley/clutter-vala,collects/clutter,heysion/clutter-clone,ebassi/clutter,djdeath/clutter-android,collects/clutter