section 4.1.1 of RFC 3875 (cgi spec) requires the server to set a AUTH_TYPE env declaring the type of authentication used. (see http://tools.ietf.org/html/rfc3875#page-11 and the comments I provided in the attached diff)
I set the ticket priority to high because this bug broke MoinMoin? w/ HTTP Authentication and I'm sure there are other apps that depend on AUTH_TYPE being set to function properly.
This is my first contribution to an open source project (this was a find and then copy/paste), but look forward to more so please let me know if I'm using proper procedure and etiquette.