title: Improving window resize behaviour, possibly by manually setting bigger framebuffer size
body: <p>I was considering using glfw in my application, while developing on mac</p>
  
  <p>After successfully writing a very simple program to render a triangle on a colored backround,
  I noticed that when resizing the window, it takes quite some time to rerender the scene, as I suspect due to framebuffer resize.</p>
  
  <p>This is not the case when I am repeating the experiment with NSOpenGLView. Is there a way to hint glfw to use bigger framebuffer size on start, to avoid expensive resizes?</p>
  
  <p>I am using GLFW 3.</p>
  
  <p>Could you also help me with enabling High DPI for retina display. Couldn't find something in docs on that, but it supported in version 3.</p>