[WINLOGON]

- CreateUserEnvironment: if user impersonation fails, just fail the call.
- SetDefaultLanguage: Use the *correct* HKEY_CURRENT_USER key to retrieve the lang., that is, first impersonate the user, then, call RegOpenCurrentUser. We do that because otherwise calling RegOpenKey(Ex) for HKEY_CURRENT_USER just uses the process cached value of HKEY_CURRENT_USER, which does not change *even if* one impersonates an user.

[MSGINA]
- Correctly impersonate the user when opening & initializing the shutdown dialog (in the same way as winlogon does), i.e. call ImpersonateLoggedOnUser and use RegOpenCurrentUser.
- Fill few (but not all) code holes in WlxScreenSaverNotify.

svn path=/trunk/; revision=72737