title: cocos2d director flow control: replace scene after push scene. What happens to the pushed scene?
body: <pre><code>// TRY TO AVOID A BIG STACK OF PUSHED SCENES
  -(void) mainMenu()
  {
      // etc
      [[CCDirector sharedDirector] pushScene: gameScene];
  }
  // stack:
  //   . game  &lt;-- running scene
  //   . mainMenu
  
  -(void) game
  {
      [[CCDirector sharedDirector] pushScene: gameOverScene];
  }
  // stack:
  //   . gameOver  &lt;-- running scene
  //   . game
  //   . mainMenu
  
  -(void) showGameOver
  {
      [[CCDirector sharedDirector] pushScene: hiScoreScene];
  }
  // stack:
  //   . scores  &lt;-- running scene (4 pushed scenes... expensive)
  //   . gameOver
  //   . game
  //   . mainMenu
  
  -(void) toMainMenu
  {
      [CCDirector sharedDirector] replaceScene: mainScene];
  }
  // stack:
  //   I don't know...
  </code></pre>
  
  <p>I want to kill all the scenes in the stack after replaceScene: call. But I don't know if it happens. </p>