Pass an Interactor to new_connection().

Thanks to the previous commit, this new parameter can replace two of
the existing ones: instead of passing a LogPolicy and a Seat, we now
pass just an Interactor, from which any proxy implementation can
extract the LogPolicy and the Seat anyway if they need it.

proxy/noproxy.c

@@ -20,7 +20,7 @@ SockAddr *name_lookup(const char *host, int port, char **canonicalname,
 Socket *new_connection(SockAddr *addr, const char *hostname,
                        int port, bool privport,
                        bool oobinline, bool nodelay, bool keepalive,
-                       Plug *plug, Conf *conf, LogPolicy *lp, Seat **seat)
+                       Plug *plug, Conf *conf, Interactor *itr)
 {
     return sk_new(addr, port, privport, oobinline, nodelay, keepalive, plug);
 }