Reorder files in .asd to get rid of warnings

Because of the whitespace noise, this is what changed:

- font-rendering.lisp moved from close to the bottom to the top.
- bindings.lisp and events.lisp moved before window.lisp.
Ignore unused variable name

This gets rid of the last style warning on SBCL
Merge pull request #152 from jorams/fix-warning

Get rid of warnings during compilation