auth: remove AuthToIDFunc and associated functions. Not used anymore.

And the current code for MitToId has a use-after-free() issue.

[Also remove the actual implementations - ajax]

Signed-off-by: Matthieu Herrb <matthieu@herrb.eu>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
(cherry picked from commit 2855f759)