End the sending of data to the remote server. This is done by ensuring that
the data already sent ends with CRLF then sending '.CRLF' to end the
transmission. Once this data has been sent <A HREF="#item_dataend"><CODE>dataend</CODE></A> calls <A HREF="#item_response"><CODE>response</CODE></A> and
returns true if <A HREF="#item_response"><CODE>response</CODE></A> returns CMD_OK.