title: MigLayout issue while setting position explicitly
body: <p>I have a problem in MigLayout when setting the position of a component explicitly (with id.x and id.y constraints) and resizing the container where the component is added. Here is a SSCCE:</p>
  
  <pre><code>import java.awt.event.KeyEvent;
  import java.awt.event.KeyListener;
  import java.awt.event.MouseEvent;
  import java.awt.event.MouseListener;
  
  import javax.swing.JFrame;
  import javax.swing.JLabel;
  import javax.swing.JPanel;
  import javax.swing.JTextField;
  
  import net.miginfocom.swing.*;
  
  public class MigClass extends JFrame {
  
      MigClass(String title) {
          super(title);
          MigLayout layout = new MigLayout();
          setLayout(layout);
          final JPanel content = new JPanel(new MigLayout()); 
  
          final JLabel l1 = new JLabel("A label");
          content.add(l1, "push, center, top, id l1");
          l1.addMouseListener(new MouseListener() {
              @Override
              public void mouseClicked(MouseEvent e) {
                  final JTextField editor = new JTextField(5);
                  content.add(editor, "pos l1.x l1.y");
                  editor.setVisible(true);
                  l1.setVisible(false);
                  editor.addKeyListener(new KeyListener() {
                      @Override
                      public void keyTyped(KeyEvent e) {
                      }
  
                      @Override
                      public void keyPressed(KeyEvent e) {
                          if(e.getKeyCode() == (KeyEvent.VK_ENTER)) {
                              l1.setText(editor.getText());
                              editor.setVisible(false);
                              l1.setVisible(true);
                          }
                      }
  
                      @Override
                      public void keyReleased(KeyEvent e) {
                      }                   
                  });
              }
  
              @Override
              public void mousePressed(MouseEvent e) {
              }
  
              @Override
              public void mouseReleased(MouseEvent e) {
              }
  
              @Override
              public void mouseEntered(MouseEvent e) {
              }
  
              @Override
              public void mouseExited(MouseEvent e) {
              }
  
          });
          add(content, "grow, push, span");
          pack();
          setVisible(true);
      }
  
      public static void main(String[] args) {
          MigClass gui = new MigClass(null);
      }
  }
  </code></pre>
  
  <p>The <code>JTextField</code> editor hasn't the right position (it should overlap l1's position) if the constraint <code>"push"</code> is added to the label (this happens only if the frame is enlarged). How can I solve this problem?</p>