Error message was not displayed, because IFTI doesn't work with classes.

dmd 2.065.0 issued 'Error: class mysql.db.MysqlDB() is used as a type' instead of the static assert.
As there is AFAIK no way to trigger the static assert on class instantiation, this turn it into an undefined symbol.
Merge pull request #31 from Geod24/mysql-error-message

[Trivial] Error message was not displayed