macosx: allow multiple vout windows in video-wallpaper mode
macosx: allow multiple vout windows in video-wallpaper mode

(first window as wallpaper, all other ones as normal windows.)

vlc-mirror/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc,krichter722/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,shyamalschandra/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,vlc-mirror/vlc,xkfz007/vlc,vlc-mirror/vlc,xkfz007/vlc,krichter722/vlc,krichter722/vlc,xkfz007/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc,xkfz007/vlc,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,krichter722/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,krichter722/vlc,vlc-mirror/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,xkfz007/vlc,krichter722/vlc,krichter722/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1