[WIP] MySQLi support for PDO::PARAM_LOB

This PR aims to resolve the issue #9 by adding the support for `PDO:PARAM_LOB` in the MySQLi adapter.

Things to do :
 * :ok: use `send_long_data` on parameters exceeding the `max_allowed_packet` size;
 * adding some tests;
 * refactoring and cleaning.