2.9.1 (unstable):

* slot: Allow sigc::slot<R(Args...)> syntax, like std::function,
  deprecating the sigc::slot<R, Args...> syntax.
  (Murray Cumming, Kjell Ahlstedt) Bug #763393
* signal: Allow sigc::signal<R(Args...)> syntax, like std::function,
  deprecating the sigc::signal<R, Args...> syntax.
  (Murray Cumming, Kjell Ahlstedt) Bug #763393


2.8.0 (stable):