By Lucia Mutikani WASHINGTON, Dec 10 (Reuters) - U.S. labor costs increased slightly less than expected in the third quarter as a softening labor market curbed wage growth, which bodes well for the inflation outlook. The report from the Labor Department on Wednesday followed on the heels of data on Tuesday showing resignations ​dropped to a five-year low in October. That supported views by Federal Reserve officials that the labor market was not a source of inflation. The labor market ‌is easing amid low ...