* NEWS: New option --atime-preserve=system, which uses O_NOATIME.

* NEWS: New option --atime-preserve=system, which uses O_NOATIME.

* configure.ac: Prefer AC_CHECK_HEADERS_ONCE to AC_CHECK_HEADERS.
Check for stropts.h and sys/filio.h too, for _FIOSATIME.
* doc/tar.texi: Change "modification time" to "data modification
time", "change time" to "status change time", and "filesystem" to
"file system", so that we use terminology consistent with POSIX.
Use American spacing rather than French for sentence ends.
"non-dependable" -> "undependable".
(Option Summary, Attributes): Explain better the pitfalls of the
--atime-preserve option, and suggest read-only mounts,loopback
mounts, and noatime mounts for older systems.
* doc/value.texi (op-atime-preserve-system): Renamed from
op-atime-preserver-system to fix a misspelling.
* src/common.h (enum atime_preserve): Use lower case for enum values.
* src/compare.c: Don't include utimens.h; no longer needed.
(diff_file): Use set_file_atime rather than utimens; avoid closing
diff_handle until after this, so that we can set the file time stamp
via the file descriptor rather than via its name.
* src/create.c: Don't include utimens.h; no longer needed.
(dump_regular_finish): Remove.  All callers now do its work inline.
(dump_dir): New arg FD.  All callers changed.
Use fdsavedir rather than savedir.
(unknown_file_error): Arg is a const pointer now.
(dump_file0): 2nd arg is a const pointer now.
Treat directories more like files, with respect to --atime-preserve.
For example, also warn if a directory changes while we are dumping it.
Prefer file descriptors to file names when retrieving/setting file
attributes; this saves path-resolution time and allows us to avoid
changing mtime/ctime on Solaris when restoring atime as root.
Use O_DIRECTORY when opening directories, to avoid some race conditions.
Do not reset atime if mtime has changed.  Report an error if
we cannot reset atime.

First cut at adding support for --atime-preserve=system.
* doc/tar.texi (Option Summary): First cut at documenting it.
All other uses of --atime-preserve changed to --atime-preserve=replace.
* doc/value.texi (op-atime-preserve-replace, op-atime-preserver-system):
New.
(op-atime-preserve): Mention METHOD.
* src/common.h (atime_preserve): New enum.
(atime_preserve_option): Now of the enum type rather than bool.
All uses changed.
* src/compare.c (diff_file): Read with O_NOATIME if asked for.
* src/create.c (dump_file0): Read regular and CTG files with O_NOATIME
if asked for.
* src/tar.c (usage): Mention new usage.
(parse_opt): Parse new usage.