Add model XD-B9800 to models.txt

Signed-off-by: Brian Johnson <brijohn@gmail.com>
Handle different encodings for add-on names based on dictionary region.

Chinese - GB2312
Japanese - Shift JIS
All others UTF-8

Don't have access to any non Japanese/Chinese devices, so unable
to test which encoding they use. Default to UTF-8 currently.

Signed-off-by: Brian Johnson <brijohn@gmail.com>