#22 configure: Add AC_HEADER_MAJOR to find where major() is defined

[Whissi]

Hi,

on Gentoo we apply the attached patch to address the problem that major() is now longer provided by glibc-2.23's mkdev.h. See https://sourceware.org/ml/libc-alpha/2015-11/msg00253.html and https://bugs.gentoo.org/580922 for details.