HTRequest only holds a single auth scheme (Was: Kerberos...)

The apache mod_auth_kerberos module by default has two
WWW-Authenticate headers, one for "Negotiate", and one for "Basic".  I
believe this is the default behaviour for IIS as well.

However the HTRequest structure only has room for a single
authentication scheme, so the last WWW-Authentication header ("Basic"
in this case) overwrites any previous values set.

This means that my functions set with a call to HTAA_newModule(), are
only called when I switch off password authentication.