user32: Enable IsDialogMessageA() ASCII to Unicode mapping only when the user default lang ID is CJK.

Using GetSystemMetrics(SM_DBCSENABLED) may incorrectly enable ASCII to Unicode mapping in mixed
locale environments. For example, when UserDefaultLCID is French(040c) but SystemDefaultLCID is
Japanese(0411).

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55655