iauth_loc: Pass ? for clients with unknown user and host names.
We previously used . for unknown hostnames, but never passed along
clients with unknown usernames. The only cue we have from ircu that
a client's ident check failed is the hurry-up (H) command, so use
that to bypass the requirement to have hostname and ident.
Signed-off-by: Michael Poole <firstname.lastname@example.org>