GUNPOWDER, THREE-PART HISTORICAL THRILLER STARRING KIT HARINGTON, PETER MULLAN, MARK GATISS AND LIV TYLER, DEBUTS DEC. 18, EXCLUSIVELY ON HBO IN THE U.S. Every year on Nov. 5 the English mark the discovery of the Gunpowder Plot in London in 1605 with bonfires and fireworks. Though known as Guy Fawkes Day because many people believe Fawkes devised …