Added property used to show another window when a window is activated.

git-svn-id: http://yate.null.ro/svn/yate/trunk@5570 acf43c95-373e-0410-b603-e72c3f656dc1
Show main window when incoming call notification window become active (MacOS only).

git-svn-id: http://yate.null.ro/svn/yate/trunk@5571 acf43c95-373e-0410-b603-e72c3f656dc1