(Reuters) - The Duke and Duchess of Cambridge are really getting dolled up for the first anniversary of their royal wedding. Mattel Inc, the U.S. maker of Barbie dolls, said this week it will release a special two-doll set this April to mark the one-year anniversary of Prince William and Kate Middleton's wedding at Westminster Abbey. The figures, part of Mattel's Barbie Collector series, will come dressed up in doll versions of the duds the couple wore in a ceremony that was viewed by an estimated 3 billion people worldwide. ...