Using hooks to change "Individual Prefix" to an auto-complete text input

Originally posted at TwoMiceAndAStrawberry.com. I recently had to modify CiviCRM to support a specific use case for a client. In this project I needed to allow the user to enter anything in the Individual Prefix field, rather than choosing from a list of options. The client in this case was very sensitive about presenting the individual's honorific precisely as the individual wants, so that "Dr.," "Rev. Dr.," and "Most Rt. Rev. Dr." should all be possible, along with anything else the user might want to enter.