* emacs.c (main): Print and error and exit when no data is read

* emacs.c (main): Print and error and exit when no data is read
from the pipe.

* startup.el (command-line): Do not mention the server name in
case the user has not mentioned it, print a more explicit message.

* emacsclient.c (start_daemon_and_retry_set_socket): Improve error
checking.