Session database driver BUG

Hello, yesterday I was working with codeigniter 3.0.0. I made a system user to review new features, and I found a bug when you share session based on a table of mysql codeigniter, MySQL returns an error. The error is given because the class system/libraries/Session/driversSession_database_driver.php in the driver database is referring to "mysql" and not "mysqli". I you replace all "mysql" with "mysqli" it runs perfectly.

I hope my contribution helps someone else if they encounter this problem.