The pr #1870 introduced safe_f! macro, which made some functions like
WIFEXITED and WEXITSTATUS const and safe on linux_like platform only,
which causes inconsistency when trying to use those functions in crates
compiled across multiple platforms, as using unsafe on those functions
will generate unused_unsafe warning on linux platforms and lack of
unsafe block will fail compilation on non-linux platforms.

To avoid the inconsistency, this commit applies the same macro for all
the same functions on other platforms too.