Handle unexposed for struct declaration.
Include wchar.h instead of io.h for CRT functions because it is a more general header.
Don't process multiple files because they may have duplicated declarations.
Remove _fdopen because mode has only ascii characters.
Create windowsu.h (close gh-9).
Disable conversion for ShellMessageBoxW() because it is not in default libs.
Fix typos.
Make compilable and runnable test exe.