Invalid MySQL syntax for date comparison

[PRGfx]

The date functions used in the MysqlQueryBuilder are copied from the SqliteQuerybuilder but don't work with mysql:

- sprintf("datetime(`%s`) %s strftime('%s', '%s')", $propertyName, $comparator, '%Y-%m-%d %H:%M:%S', $propertyValue->format('Y-m-d H:i:s'));
+ sprintf("`%s` %s str_to_date('%s', '%s')", $propertyName, $comparator, $propertyValue->format('Y-m-d H:i:s'), '%Y-%m-%d %H:%i:%S');

str_to_date takes the format as the second argument and minutes are %i.
Unfortunately I don't see a good solution for the first datetime call, as the format depends on the indexing configuration on the property. In my tests I got the impression that there is some implicit type conversion happening, but I'm not sure if that's really what's going on.