MEXICO CITY, — With a presidential election approaching, the crowds assembling here Tuesday for International Workers’ Day — or May Day, as it’s know the world over — were more animated than usual, the floats and rallies resembling performance art. Thousands poured into Mexico City’s main square, the Zocalo, to hang in effigy the wage-killing labor reforms of outgoing President Enrique Peña Nieto and depict the suffering and struggle of Mexico’s workers. A giant lemur wearing prison stripes represented the oligarchs who privatized the country’s telecommunications industry.