Dumps broken when not using PDO driver

When creating dumps using a non-PDO database driver (i.e., either mysql or mysqli), the created dumps contain erroneous table definitions:

CREATE TABLE xyz (
  ...
) ENGINE=MyISAM;
ENGINE=MyISAM;

This bug was introduced when special code for PDO was backported from HEAD, which indeed returns incomplete table definitions. However, since the native MySQL drivers are not affected, output is now broken for D6.

Committed the attached patch.