Patched demo to work with newer GLFW/OpenGL.

Tested with GLFW   == 0.5.2.0,
            OpenGL == 2.8.0.0.

Newest OpenGL use StateVar mechanism to simplify API.
It also allows to set window size in openWindow function,
instead of using GLFW hints.
Merge pull request #8 from mgajda/master

Patched demo to work with newer GLFW/OpenGL.