... to factor out fix for glibc 2.25 introduced in 7a5b301e3 (build: Use
AC_HEADER_MAJOR to find device macros).
Note: Once glibc 2.25 is old enough and this fix is not needed also
AC_HEADER_MAJOR in configure.ac should be removed.
Signed-off-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>