paint-volume: Use the correct coordinate for axis alignment
paint-volume: Use the correct coordinate for axis alignment

The z coordinate of the origin should be checked against the same
coordinate of the vertex behind it. Given that most actors are flat
surfaces, this check should always succeed.

https://bugzilla.gnome.org/show_bug.cgi?id=675396

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