Fixed ubraces alignment for the listing "A function declaration".

First off, I don't know if this is a fonts related issue (or anything else) or really a misalignment in the book.
I attach screenshots to show how it looks before & after on my system.
It would be great if anybody can confirm/refute this bug on their system.

Broken:
![broken](https://f.cloud.github.com/assets/994128/550757/b23e2a74-c319-11e2-9c32-0c3d288b7f39.png)

Fixed:
![fixed](https://f.cloud.github.com/assets/994128/550759/b69cc85a-c319-11e2-8edd-141984f1647e.png)