Nikkei ekes out gains, may extend winning streak to 11th day
* Nikkei may extend rally into 11th day, longest since 1988 * Market looks set to log fifth straight month of gains * Power, gas companies one of the best performer this month * Yahoo Japan jumps on China business plan By Hideyuki Sa** TOKYO, May 29 (Reuters) - Japan's Nikkei share average edged up on Friday on hopes of better shareholder returns, looking set to extend its winning streak to 11 straight sessions and its fifth straight month of gains. The Nikkei average ro