* lib/utime.in.h: Include next <utime.h> if it exists.
(utimbuf): Define to _utimbuf on native Windows.
* m4/utime-h.m4 (gl_UTIME_H): Check for prerequisites of include_next.
Set UTIME_H on native Windows.
(gl_UTIME_MODULE_INDICATOR, gl_HEADER_UTIME_H_DEFAULTS): New macros.
* modules/utime-h (Depends-on): Add include_next.
(Makefile.am): Substitute also HAVE_UTIME_H, INCLUDE_NEXT,
PRAGMA_SYSTEM_HEADER, PRAGMA_COLUMNS, NEXT_UTIME_H.