JOHANNESBURG (AFP) — South Africa, the continent's economic powerhouse, is braced for a slowdown after a stretch of solid growth, as higher interest rates coupled with rising food and fuel costs are set to bite. Growth in the first quarter measured 2.1 percent on a 12-month basis, down sharply from 5.3 percent in the last quarter of 2007, government statistics show. The dip has been blamed on energy constraints which led to massive power cuts that forced mines and other industries to shut down. The country's economy has been growing at an average of three percent since the end of...