THE problem - as Mayan apocalypse expert Robert Bast puts it - is that if you build it, they will come. And that's why the man who wrote the book on the impending end of the world - due either tomorrow or Saturday Australia time, depending on which time zone you believe it will strike in first - won't show you his doomsday bunker. Asked to take us to the safe house he and his wife and three children will be fleeing to on Friday, he was adamant that its location had to remain secret. ''I've turned down every request...