build: Use AC_HEADER_MAJOR to find device macros

build: Use AC_HEADER_MAJOR to find device macros

Depending on the OS/libc, device macros are defined in different
headers. This change ensures we include the right one.

sys/types.h - BSD
sys/mkdev.h - Sun
sys/sysmacros.h - glibc (Linux)

glibc currently pulls sys/sysmacros.h into sys/types.h, but this may
change in a future release.

https://sourceware.org/ml/libc-alpha/2015-11/msg00253.html