Roger Gros, publisher of Global Gaming Business magazine, said a casino marketing war has broken out in a fierce battle for customers. The car giveaways, cheap buffets and slot bonuses that have been a staple of casino promotions in the past are being overshadowed by new mega-sweepstakes amounting to millions of dollars in prizes. This summer, the casinos are being quite generous with their promotional offers _ commonly known as comps'' _ to draw customers to Atlantic City. Guarantees that no one loses at the slot machines.