Stocks added to their win streak as the major indexes again finished up for the week. The Nasdaq, which gained 0.1% Friday, now has risen for four weeks in a row. The S&P 500 and the NYSE composite edged up 0.2% Friday while extending their weekly win streaks to five weeks. The IBD 50 slipped 0.3% Friday. Volume was down across the board for a third straight day. Weekly volume also fell on both major exchanges. Leading stocks were mostly quiet,