Unable to use full name with apostrophe as username

Since the pattern at acquia.com was to use full names as user names, I attempted to change my username to "Chuck D'Antonio" and got an error that the name was illegal. After some digging, I noticed it was not an issue with the site but was part of core that an apostrophe was not an accepted character and remains in 7.x. I put together a quick patch to add the apostrophe character to the set of acceptable characters.