Display hostname and port in getaddrinfo() error message.

Just reporting the error without the parameter value that causes it
makes it hard to see why there is a problem.

I spotted this trying to use ; (the correct one was #) to comment
lines in dvblast.conf and suddenly dvblast started complaining
about getaddrinfo() errors.
Fix setting of source specific multicast (SSM).

It was reported that setting SSM address doesn't work. This
patch fixes it.

Reported-by: Kristian Pedersen <kristian.pedersen@vejen-net.dk>