By Karolos Grohmann RIO DE JANEIRO, Aug 7 (Reuters) - Strong winds wreaked havoc at the Rio Olympics on Sunday, forcing the cancellation of the rowing competition and delays to tennis and kayaking, while spectators ran for cover from flying debris on the second full day of competition. Powerful gusts swept across the Brazilian city, ripping a large banner off the aquatics centre, triggering the closure of souvenir shops in the Olympic park and forcing organisers to reschedule events. Rowers were told to stay off the water at the Rodrigo de Freitas Lagoon a day after difficult conditions on the opening programme on Saturday led to complaints from rowers that races should have been postponed after one boat capsized. More...