VLCMediaPlayer: clarify the documentation for the audio and spu getters/setters
VLCMediaPlayer: clarify the documentation for the audio and spu getters/setters

CollabraMusic/VLCKit,waterskier2007/VLCKit,CollabraMusic/VLCKit,larrytin/VLCKit,brion/VLCKit,strukturag/VLCKit,hpsoar/VLCKit,simon1984/test,kamcord/VLCKit,strukturag/VLCKit,CollabraMusic/VLCKit,siuying/VLCKit,siuying/VLCKit,programming086/VLCKit,simon1984/test,i386/vlckit,programming086/VLCKit,hpsoar/VLCKit,kamcord/VLCKit,waterskier2007/VLCKit,siuying/VLCKit,waterskier2007/VLCKit,larrytin/VLCKit,simon1984/test,kamcord/VLCKit