Update Mainpage.dox with new authors.
Update Mainpage.dox with new authors.

shadeslayer/phonon-gstreamer,KDE/phonon-directshow,KDE/phonon-gstreamer,KDE/phonon-waveout,KDE/phonon-gstreamer,KDE/phonon-mmf,shadeslayer/phonon-gstreamer,KDE/phonon-xine,KDE/phonon-directshow,shadeslayer/phonon-gstreamer,KDE/phonon-xine,KDE/phonon-xine,KDE/phonon-quicktime