libvlc: factor input_item_preparsed_changed
libvlc: factor input_item_preparsed_changed

And don't re-send event, even if this can't happen with current vlc core.

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc