David Gilmour’s historic return to Pompeii, site of one of the greatest achievements in Pink Floyd’s history, will be documented in a one-night-only film coming to theaters on September 13. Live at Pompeii will recall Gilmour’s two shows at the amphitheater back in July as he supported 2015’s Rattle That Lock on a massive world tour. 45 years prior, Pink Floyd played arguably their most famous…