Britney Spears has a wild Friday night lined up ... complete with buttered popcorn, Slurpees and a movie theater screening of "The Devil Wears Prada 2." The pop icon just shared a wild video, which sure seemed to be in her car, apparently on the way to the theater ... and she says she's going to chow down on popcorn with loads of butter and wash it all down with an iced beverage. Worth noting ... it appeared Brit was in the driver's seat when she made the video. Britney says she's buying a