Fix test when using libmysqlclient

TL;DR
When suing libmysqlclient, ints are fetched as strings, so the strict comparison was failing

pdo_mysql: "--" should be followed by a whitespace character

This required changing how YYFILL works, with no apparent regressions

Implemented PDO Driver specific SQL parsers

RFC: http://wiki.php.net/rfc/pdo_driver_specific_parsers