Introduce note_auth_failure hook to allow modules to add support

for additional auth types. This makes ap_note_auth_failure() work with
mod_auth_digest again.

PR: 48807


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@960399 13f79535-47bb-0310-9956-ffa450edef68