[ticket/13055] Fix string profile fields validation to support unicode

Add unicode support to the string type based profile fields.

<a href="https://tracker.phpbb.com/browse/PHPBB3-13055">PHPBB3-13055</a>.
I mean there is a difference between `\w` and `\p{L}}\p{N}`
The `\w` things already exist in 3.0, and you are simply updating them and changing them.
However not all of the custom profile fields should contain non-asci characters.

So we need to find a good way, between a-z and non-asci, or we must add all of them twice, once for a-z and once for non-asci.