* Chairman of Joint Chiefs asks pastor to not support film * Pastor agrees to 're-evaluate' showing movie By Phil Stewart WASHINGTON, Sept 12 (Reuters) - General Martin Dempsey, the chairman of the U.S. Joint Chiefs of Staff, called a Florida pastor on Wednesday and asked him to withdraw his support for a film whose portrayal of the Prophet Mohammad has been linked to violent protests - including one that ended with the death of America's envoy to Libya. "In the brief call, Gen. Dempsey expressed his concerns over the nature of the film, the tensions it will inflame and...