drag-action: Use the dragged actor private API
drag-action: Use the dragged actor private API

Use the newly added private API on ClutterStage to track the currently
dragged actor.

https://bugzilla.gnome.org/show_bug.cgi?id=652842

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