adodb upgrade

Upgraded Adodb from v4.94 (23rd Jan 2007) to v5.18 (3rd Sep 2012) - tested locally (php 5.4.7) with no issues.
note: this is a PHP 4.x breaking change, an alternative could be provided that would allow PHP 4.x functionality to remain, although this branch of adodb no longer appears to be updated.

see adodb changelog (http://phplens.com/adodb/change.log.html) for full details of changes.