Firebird keywords

[viegasfh]

There is a need to automatically quote firebird's keywords. For instance, the acts_as_list plugin uses a column position, that will not work with the current rubyfb driver.

In addition, given that support is only available for Firebird 2.0+, the first and offset should be replaced by the rows x to y. I have already done this as it was causing some trouble with will_paginate, but it would be good to add the support to the default one available in the repos.

[viegasfh]

Sorry, I meant the limit method wasn't working, hence my reason for fixing it. I have changed to rows x to y as it is more elegant.