Hi!
Why Google uses branching to such an old version? Aren't the fixed being backported to latest builds of 5.0.x (there was quite a time since 5.0.37).
Hehe, it was actually Google people who coined 'four oh forever' (a nickname for our 4.0.40 build ;-), and now they refer to their build as 'five oh forever' (probably rounding 37 to 40 ;-). Once you run software and you do quite a bit of engineering on top, you are not rushing to upgrade all the time :-) Oh, and they have quite a team of people working on improvements.
As for MySQL 6.0, maybe it's worth a dedicated Database.php class for the testing purposes..
Why? Current Database class works just fine.
Cheers, Domas