US STOCKS-S&P 500 futures rise after early signs Britain will stay in EU

* S&P 500 futures open higher after polls close
* Opinion poll puts “remain” campaign in lead
* Twilio Inc nearly doubles in welcome return of tech IPOs
* Indexes up: Dow 1.3 pct, S&P 1.3 pct, Nasdaq (NasdaqGS: NDAQ – news) 1.6 pct (Updates to after close of polls in UK)
By Rodrigo Campos
June 23 (Reuters) – U.S (Other OTC: UBGXF – news) . stock index futures opened higher in after hours trading on Thursday after polls closed in Britain with early signs that