At La Main Bleue, an outdoor club hidden in the back alleys of Brazzaville, Hassan Salvador enters like he owns not just the Congo but the world: Gianfranco Ferré umbrella stretched open overhead, though no rain is likely to fall, salmon-colored silk scarf draped on top of his tie and sport coat, though it has to be 90 degrees Fahrenheit on the terrace. Salvador, a tall 34-year-old with his head shaved shiny, prances, struts and strides between blue plastic tables covered with brown-glass bottles of beer. As all eyes turn to him, Salvador comes to a precise stop before the dance floor, stretches out his left arm so that...