Change Database.php

As far as I know and I am not an expert, the only practical difference are emoticons. Those can not be handled by UTF-8, because emoticons are 4-bytes long, and UTF-8 have characters encoded from 1-3 bytes. All usual characters, whose are with us for decades, took the same amount of space in both cases. If there is no performance downside, then default CodeIgniter's settings could be changed. For some users are emoticons the new meaning of life, so this change could avoid potential developers problems (The Story of UTF8 VS UTF8MB4).

The clue for a decision could be the reasons behind phpMyAdmin change and what are defaults in major databases (MySQL, MariaDB, PostreSQL, etc.) and other popular PHP frameworks. I would like to see some other points of view on this topic.