Rudolph W. Giuliani, clarifying once again his stance on abortion, completely accepted yesterday women's ''right of choice'' on abortion, except for a personal disclaimer. Mr. Giuliani, who is seeking the Republican nomination for mayor of New York City, began the year advocating that the United States Supreme Court overturn the Roe v. Wade decision, which legalized abortion in 1973. Yesterday, he said he ''will oppose making abortion illegal.'' As late as last month, he said he had no position on what the Governor or the State Legislature should do about abortion. Mr. Giuliani's statement yesterday was viewed as a ''flip-flop''...