configure: Check for major() more strictly

configure: Check for major() more strictly

Thing is, in f3f15cc24 I'm trying to adapt libvirt to the newest
glibc where major()/minor()/makedev() are moved from sys/types.h
to sys/sysmacros.h. However, my commit back then expect autoconf
to be fixed too as we already use AC_HEADER_MAJOR to determine
which header file the functions are in, but because the header
files just trigger a warning and not a compile error, the
autoconf macro detects the bad header file.

This is just a workaround until autoconf macro is fixed.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>