These headers are not available on Windows. <bsd/sys/cdefs.h> ensures
that __has_include() and __has_include_next() are defined.
Signed-off-by: Guillem Jover <guillem@hadrons.org>
Glibc tends to include standard headers with special definitions
that make few declarations or macros visible, this stomps over the
overlay #include_next <> logic.
Based-on-patch-by: Robert Millan <rmh@debian.org>
