Testing Glutin back-end with "user_input"

[bvssvni]

Running the "user_input" example https://github.com/PistonDevelopers/piston-examples/blob/master/user_input/src/main.rs

On OSX 10.9.5, I get this with Glutin:

SDL2:

[bvssvni]

The red square is the window size and the blue square is the draw size.

[bvssvni]

There are two problems here:

• glutin_window includes the title bar in the size
• the viewport is offset too high

[bvssvni]

Fixed.