Adds an extra 'log' parameter to services that routes STDOUT and STDERR to syslog.
Uses a PTY rather than a pipe, as this prevents log messages hanging around in a buffer indefinitely.
In service_start() the SIGCHLD handler is reenabled before calling complete(), so the service could be reaped by the SIGCHLD handler leaving service_start() waiting forever
Also remove code that duplicates sig_unblock()
Patrick Stewart