network process timeouts

[Ted Zlatanov]

This came up as a Gnus question. I don't think Emacs today supports
connection timeouts.

Once the network connection is attempted, the control passes down to the
networking layer, which could be GnuTLS. So the timeout parameter could
be set with gnutls_handshake_set_timeout() (for which we'll need to
modify gnutls.c) or with set_socket_option(SO_RCVTIMEO/SO_SNDTIMEO) in
process.c. At the Emacs Lisp level, it would be a new parameter for
`make-network-process'.

The good news is that all packages, not just Gnus, would benefit from
that. So I think it's a good platform improvement.

If I've missed existing functionality to do network timeouts, please let
me know.

Thanks
Ted