Fix for sysinstall (please apply)

Hello,

in PR bin/59078 I have submitted a simple fix for sysinstall that allows it to 
correctly support the Greek locale. 

In every FreeBSD release so far, one cannot select a greek keymap during the 
installation and has to be aware of the ways it can be enabled afterwards. 
This however is not evident to a novice user, who (in my experience) performs 
most administrative tasks from sysinstall. Since 5.2-RELEASE is just around 
the corner, I would like to implore some kind soul to review and commit it on 
time. 

Regards,
-- 
Panagiotis Astithas
Electrical & Computer Engineer, PhD
Network Management Center
National Technical University of Athens, Greece