stage: Add :use-alpha property
stage: Add :use-alpha property

The ClutterStage:use-alpha property is used to let a stage know that it
should honour the alpha component of the ClutterStage:color property.

If :use-alpha is set to FALSE the stage always uses the full opacity
when clearing itself before a paint(); otherwise, the alpha value is
used.

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