Ticket #3857: avoid glibc 2.25 warnings about major(), minor(), and makedev().

Ticket #3857: avoid glibc 2.25 warnings about major(), minor(), and makedev().

See gnulib a512e041120e9012e69afa2f5c3adc196ec4999a:

glibc 2.25 is deprecating the namespace pollution of <sys/types.h>
injecting major(), minor(), and makedev() into the compilation
environment, with a warning that insists that users include
<sys/sysmacros.h> instead.  However, because the expansion of
AC_HEADER_MAJOR didn't bother checking sys/sysmacros.h until after
probing whether sys/types.h pollutes the namespace, it was not defining
MAJOR_IN_SYSMACROS, with the result that code compiled with -Werror
chokes on the deprecation warnings because it was not including
sysmacros.h.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>