Fix link Documentation/OpenGL 2.1 Reference Pages

Now that the url http://www.opengl.org/sdk/docs/man/ links to the reference pages for the latest version of the spec (yay!), the link for the OpenGL 2.1 ref pages needs to be fixed to: http://www.opengl.org/sdk/docs/man2/

Thanks in advance webmaster! :slight_smile:

I believe what you requested is now fixed.

Yes, it is, thank you!