windows-stat-timespec: New module. * modules/windows-stat-timespec: New file. * m4/windows-stat-timespec.m4: New file. * m4/sys_stat_h.m4 (gl_HEADER_SYS_STAT_H): Set WINDOWS_STAT_TIMESPEC. * modules/sys_stat (Makefile.am): Substitute WINDOWS_STAT_TIMESPEC. * lib/sys_stat.in.h (struct stat) [WINDOWS_STAT_TIMESPEC]: Declare with fields st_atim, st_mtim, st_ctim. (st_atime, st_mtime, st_ctime): Define as macros. (_GL_WINDOWS_STAT_TIMESPEC): New macro. * lib/stat-w32.h (_gl_convert_FILETIME_to_timespec) [_GL_WINDOWS_STAT_TIMESPEC]: New declaration. * lib/stat-w32.c (_gl_convert_FILETIME_to_timespec) [_GL_WINDOWS_STAT_TIMESPEC]: New function. (_gl_convert_FILETIME_to_POSIX): Adjust coding style. (_gl_fstat_by_handle): If _GL_WINDOWS_STAT_TIMESPEC, convert the FILETIME to 'struct timespec', not 'time_t'. * lib/stat.c (rpl_stat): If _GL_WINDOWS_STAT_TIMESPEC, convert the FILETIME to 'struct timespec', not 'time_t'. * lib/stat-time.h (STAT_TIMESPEC): Define also if _GL_WINDOWS_STAT_TIMESPEC. * doc/windows-stat-timespec.texi: New file. * doc/gnulib.texi: Include it.

@node Precise file timestamps on Windows
@section Precise file timestamps on Windows

The module @samp{windows-stat-timespec} ensures that,
on native Windows platforms, @code{struct stat} contains
@code{st_atim}, @code{st_mtim}, @code{st_ctim} fields of type
@code{struct timespec}, providing 100 ns resolution for the timestamps
of files.

Note: On some types of file systems, the timestamp resolution is limited
by the file system.  For example, on FAT file systems, @code{st_mtim}
only has a resolution of 2 seconds.  For more details, see
@url{https://msdn.microsoft.com/en-us/library/ms724290.aspx}.