Following a discussion with Alexandre on IRC, here is a revised patch. This one doesn't touch the LC_MESSAGE, as these do not affect the user locale. Further work will be necessary on supporting MUI like language checking.
Shachar Shemesh wrote:
Changelog: Shachar Shemesh winecode@shemesh.biz dlls/kernel/locale.c
- System default locale in Windows determines the ANSI encoding (LC_CTYPE on Unix)