[Dovecot] authenticate plain and utf-8 with special chars

[Matthias Lay]

Hi,

I experienced some problems with authenticate. 

seems like the mail clients like thunderbird send their base64 string in
ISO- encoding, which doesnt work on my dovecot setup if there are some
Umlauts

I am not able to login as 
 "ömer" for example


If I authenticate from telnet with an base64 encoded utf-8 string like
 'echo -en "\0ömer\0Start12" |base64'
everything works fine


-dovecot 2.1.7
-userdb is an openldap which queries an windows AD so results are in
utf8, I think.

any clues at which point to fix this are welcome ;)