Update the gl/examples to build on latest rust and glfw

[navaati]

I have not, however, been able to update the struct_triangle.rs example

[bvssvni]

Looks good.

[bvssvni]

I'm having problems building examples from the "gl" folder.

$ cargo build --example static_triangle
no example target named `static_triangle`

[tomaka]

You need to remove this line.

[bvssvni]

Both "static_basic" and "static_triangle" need to add as *const () to work.

[bvssvni]

The reason that "struct_triangle" does not work is, if I remember correctly, that generate_gl_bindings! was replaced by a build script.