Added isHiding field to _ClutterStageOSX to allow windowDidResignKey delegate to not order full screen window back whilst the full screen window was being hidden.  This caused other application windows to be hidden
Added isHiding field to _ClutterStageOSX to allow windowDidResignKey delegate to not order full screen window back whilst the full screen window was being hidden.  This caused other application windows to be hidden

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