Mac Margolis writes for Bloomberg Opinion: Running for a constitution-bending fourth term, Bolivia’s Evo Morales is still going strong. Latin America’s left-wingers are in a rut. Venezuela’s Nicolas Maduro presides over a collapsing economy behind bayonets. An Ecuadoran court has ordered the arrest of former president Rafael Correa, who is living in Belgium. Brazil’s Dilma Rousseff was impeached for…