In ucrt, this struct has a different layout, with only three fields
exposed in headers (which can be used by inline functions).

This fixes use of some ctype.h functions like e.g. _isdigit_l
from applications that use ucrt (both with MSVC and mingw-w64).
Signed-off-by: Martin Storsjo <martin@martin.st>
Signed-off-by: Piotr Caban <piotr@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>