Friends and acquaintances of Phil Yost are constantly giving him ideas for buildings, the 40-year-old architect said Monday. 'I was catching up with my old college roommate, who I hadn't spoken to in years, and he blurts out, 'What if you built a revolving hotel like they have revolving restaurants?'' Yost said. 'Do you know how many times I've gotten that?' In the past month, Yost has heard pitches for pyramid-shaped warehouses, retractable-roof golf courses, and 100-story, subterranean 'groundscrapers' that would be impervious to terrorist attack. 