actor: Use the internal child list for map/unmap
actor: Use the internal child list for map/unmap

Use the internal child list for the default map/unmap vfuncs. This removes
the requirement for non-container composite actors to implement their own
map/unmap functions.

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