crt: Use __acrt_iob_func for accessing __iob in all msvcrt versions

This makes sure that all code in libmingwex that refers to stderr
etc will work correctly even if linked to ucrtbase.

Signed-off-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Jacek Caban <jacek@codeweavers.com>
6 files changed