SANTIAGO (Reuters) - Hugo Chavez, Venezuela's cancer-stricken president, made his presence felt at a regional summit on Monday with a flowery letter from his sickbed in Cuba that was laced with literary references and calls for Latin American unity. Chavez has not been seen in public since cancer surgery in Cuba in mid-December, missing his own inauguration for a new six-year term this month and fueling uncertainty over the illness jeopardizing his 14-year rule. ...