The vorbis use flag denotes ogg/vorbis support, not the other way around (libvorbis depends on libogg).
same for media-sound/mp3splt media-sound/yammi media-sound/alsaplayer (ogg use flag superfluous) media-sound/asunder media-sound/prokyon3/
media-sound/mpd fixed ("vorbis" instead of "ogg")
media-sound/mpd-svn (not even on list) fixed too
Changing summary line to be more accurate.
alsaplayer uses ogg useflag with flac useflag to enable oggflac support, so ogg useflag there is right. Fixed yammi, mp3splt, asunder and prokyon3 (old version, newer was fixed already).