title: c++ get elapsed time platform independent
body: <p>For a game I wanna measure the time that has passed since the last frame. </p>
  
  <p>I used <code>glutGet(GLUT_ELAPSED_TIME)</code> to do that. But after including glew the compiler can't find the glutGet function anymore (strange). So I need an alternative. </p>
  
  <p>Most sites I found so far suggest using clock in ctime but that function only measures the cpu time of the program not the real time! The time function in ctime is only accurate to seconds. I need at least millisecond accuracy. </p>
  
  <p>I can use C++11.</p>