[SCIM] New skim po file

[LiuCougar]

Hi,

I just added translator information in the skim about dialog, and
modified ko.po, ja.po and zh_CN.po accordingly.

So Kitae and Yukiko, could you check it? (right click menu of system
tray icon -> About skim -> Translator)

Also, fixed a bug in one Makefile.am which causes missing 4
translation strings. Please translate them too.

Thanks,
Cougar
-- 
"People's characters are strengthened through struggle against
difficulties; they are weakened by comfort."
- Old Chinese adage