[macosx] Wrong rendering of diacritics on macOS

Wrong rendering of diacritics on macOS

Reproduced on 8u112 on a Mac running Sierra (10.12.1)

public class LabelWithDiacriticTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JLabel label = new JLabel("au0300"); // a with grave accent
            label.setFont(new Font("Menlo", Font.PLAIN, 24));
            JFrame frame = new JFrame();
            frame.add(label);
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        });
    }
}

To reproduce the issue, run the attached sample program. It's expected to
show text label with 'a' character, with grave accent applied. Instead it
shows label with 'a' and grave accent rendered separately.