re-Captcha module enabled

i've enabled the recaptcha module, in place of the standard captcha. The difference is that Recaptcha draws extracts from texts in the Internet Archive and presents them to 'solve' rather than randomly munged text. each solution, is a contribution to better texts in the Internet Archive.

the standard module doesn't support theming, so it's a bit jarringly burnt orange, but, it's for a good cause (and we've requested support for theming).

/jt