Mariah Carey is being sued for copyright infringement over her song ‘All I Want For Christmas Is You’. The hit has become a festive staple since it was released in 1994 but Mariah and her co-writer Walter Afanasieff are being sued for $20 million by songwriter Andy Stone – who claims that he co-wrote a track of the same name in 1989. In legal documents filed in Louisana, Stone claims that he has never given permission for the track to be used and argues that Mariah and her collaborators “knowingly, wilfully, and intentionally engaged in a campaign” to infringe his copyright. Stone accuses the …