box: Let pack_at() create the ChildMeta, if any
box: Let pack_at() create the ChildMeta, if any

A sub-class of ClutterBox might add ChildMeta support, and since
pack_at() does not go through clutter_container_add_actor(), we
need to manually call the create_child_meta() ourselves.

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