Initialise the box allocation
Initialise the box allocation

We need the allocation to be < 0 for the subclasses to compute it
correctly the first time.

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