Some system properties (user.lanaguage, user.region, user.country) should be readonly if we don't support the value change on the fly.

Platform: any
JDK version: build 1.4.0beta-b28
Locale: any

To reproduce this problem on Win2000:
- On Win2000, set both default system language and locale to "English"
- java -Duser.language=ja GetUserOptions
- you will get results like:
default locale= ja_US
user.language= ja
user.country= null
user.region= US


Obviously, JDK can not pick up the new system properties value which user set on the fly. If we don't support it, we should make them read only.