(LEAD) (Olympics) European Tour young gun arrives in Rio, eyes Olympic medal

(ATTN: CHANGES dateline; UPDATES updates in lead, para 2; ADDS more info in paras 9-11)

RIO DE JANEIRO, Aug. 9 (Yonhap) -- An Byeong-hun, South Korean young gun on the European Tour, arrived in Rio de Janeiro, eyeing a medal in golf's long-awaited ret