LONDON (Reuters) - American rapper Dr. Dre has hip-hopped over strict Olympic marketing rules by giving his high-end headphones to athletes, with officials on Friday ruling this did not breach guidelines. The International Olympic Committee (IOC) forbids athletes from taking part in advertising for anyone except the 11 international companies that pay around $100 million each for four years of global rights to sponsor the Olympics. The rules are designed to prevent "ambush marketing", or non-sponsors getting free publicity on the back of the Games. ...