Open a TLS connection for a port to a host.
Returns a subprocess object to represent the connection.
Input and output work as for subprocesses; `delete-process' closes it.
Args are NAME BUFFER HOST PORT.
NAME is name for process. It is modified if necessary to make it unique.
BUFFER is the buffer (or `buffer-name') to associate with the process.
Process output goes at end of that buffer, unless you specify
an output stream or filter function to handle the output.
BUFFER may be also nil, meaning that this process is not associated
with any buffer
Third arg is name of the host to connect to, or its IP address.
Fourth arg PORT is an integer specifying a port to connect to.
If `starttls-use-gnutls' is nil, this may also be a service name, but
GnuTLS requires a port number.
(fn NAME BUFFER HOST PORT)