How to make registration Salutation field optional?

Greetings!
The salutation field can be set false from Admin/Configuration/Customer Details, but how to make it optional (i.e. still shown but not required).
I think includes/modules/create_account.php need to be modified a little bit, but don't know exactly which line and how?
Please help. Thank you.

Take a look in similar threads below.

The salutation is one of the fields that's either on or off, due to its implementation (it's presented as a pair of radio-buttons).

Any change to that behavior will require a change to many, many more modules than /includes/modules/create_account.php, just go to your admin's Tools->Developers Tool Kit and, in the last selection, enter **gender **and search in all catalog/admin files.

Wow, that's scary. There are 60+ files involved.
Hope new version of Zen Cart could be more flexible, because some websites do leave the salutation field optional, and also because gender is growing vague nowadays.