stage: Add :key-focus property
stage: Add :key-focus property

ClutterStage has both set_key_focus() and get_key_focus() methods, but
there is no :key-focus property. This means that it is not possible to
get notifications when the key-focus has changes except by connecting to
both the ::key-focus-in and ::key-focus-out signals and do additional
bookkeeping.

http://bugzilla.openedhand.com/show_bug.cgi?id=1956

Signed-off-by: Emmanuele Bassi <049ee2061f71220e5aaf33f5be422fc2a2b06a44@linux.intel.com>

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