BARCELONA, Nov 15 (Reuters) - Leading European publishers are coming to terms with what teenage boys and men have known for years -- the Web beats magazines in grabbing their eyeballs. Magazine publishers such as London-based media group Emap (EMA.L: Quote, Profile, Research), Germany's Axel Springer (SPRGn.DE: Quote, Profile, Research) and France's Lagardere have seen a split growing in their...