_filter_dup(): check streams.
_filter_dup(): check streams.

Based on John Stebbins's patch.

koying/libbluray,UIKit0/libbluray,EdwardNewK/libbluray,mwgoldsmith/bluray,Distrotech/libbluray,vlc-mirror/libbluray,vlc-mirror/libbluray,ace20022/libbluray,mwgoldsmith/bluray,Distrotech/libbluray,koying/libbluray,EdwardNewK/libbluray,mwgoldsmith/bluray,ShiftMediaProject/libbluray,UIKit0/libbluray,koying/libbluray,vlc-mirror/libbluray,UIKit0/libbluray,Distrotech/libbluray,vlc-mirror/libbluray,Azzuro/libbluray,koying/libbluray,Distrotech/libbluray,EdwardNewK/libbluray,EdwardNewK/libbluray,ShiftMediaProject/libbluray,ace20022/libbluray,ace20022/libbluray,tourettes/libbluray,tourettes/libbluray,ace20022/libbluray,ShiftMediaProject/libbluray,Azzuro/libbluray,Azzuro/libbluray,tourettes/libbluray,mwgoldsmith/bluray,tourettes/libbluray,ShiftMediaProject/libbluray,UIKit0/libbluray,Azzuro/libbluray