The outing of an Icelandic woman as the snitch who dimed out Southie mobster James “Whitey” Bulger could put her in danger and may have a chilling effect on other witnesses who could think twice before coming forward, former prosecutors warn....The FBI — which vowed confidentiality to the tipster — also could take a hit if it comes out that the agency was involved in the leak.The woman’s identity was made public yesterday in a Boston Globe story on Bulger’s life of the lam. Her background, photo, husbands, career and $2 million reward were detailed by the newspaper and now...