David Arquette has backed up Jennifer Aniston’s Oprah Winfrey show claims that she is “still on” with Vince Vaughn. David, husband of Courteney Cox-Arquette, told LA radio station STAR 98.7, that the break-up rumours are: "complete horse doo-doo. It’s so funny, they say stupid things like, ’Why’d Vince leave?’ or…