title: Query highest supported OpenGL version before context initialization?
body: <p>I want to know if there is a way (ideally cross platform, but if not just POSIX compliant or at least in Linux) to query for the highest supported OpenGL version in the current system.</p>
  
  <p>I would like to be able to instantiate GLFW windows to be the highest supported version, rather than blindly trying different versions until one allows for valid context initialization.</p>
  
  <p>EDIT:</p>
  
  <p>Assume I am not creating a context. Imagine I want to replicate what glxinfo does. In other words, I want to be able to query the installed OpenGL version without EVER creating a context.</p>