When the passthru_thead is running, the protocol (%p) command-line specifier
will now expand to "raw" rather than "telnet/rlogin/ssh". This disables IAC handling in sexpots, for example, which isn't needed or desired when using the passthru socket. Also, put some conditional checks for passthru_thread_running in external() and if it's not (e.g. for testing purposes), then lock the input_thread_mutex instead of changing passthru_socket_active. This is currently just a way to easily test the differences between direct and passthru socket I/O (dependant on whether or not the passthru_thread is running which is controlled in main.cpp.