osx/stage: Synthesize an enter event on show
osx/stage: Synthesize an enter event on show

If the pointer is inside the window frame when it's shown then we need
to synthesize and emit a NSMouseEnterEvent ourselves, as Quartz won't
do it for us.

This is a bit of a blind commit - but it's taken from an equivalent
patch that has been verified to work in GDK.

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