Fix #345: add accessor for #ysession.opaque
Fix #345: add accessor for #ysession.opaque

leoliu/yaws,sebgod/yaws,klacke/yaws,sebgod/yaws,klacke/yaws,klacke/yaws,phonohawk/yaws,leoliu/yaws,sebgod/yaws,sebgod/yaws,phonohawk/yaws,klacke/yaws,phonohawk/yaws,klacke/yaws,leoliu/yaws,phonohawk/yaws,phonohawk/yaws,leoliu/yaws,klacke/yaws,phonohawk/yaws,leoliu/yaws,leoliu/yaws,sebgod/yaws,leoliu/yaws,sebgod/yaws,klacke/yaws,sebgod/yaws,phonohawk/yaws