Import from coreutils.

Import from coreutils.

* MODULES.html.sh: Add mkancestors.
* modules/mkancesdirs: New module.
* modules/mkdir-p (Files): Remove lib/chdir-safer.c, lib/chdir-safer.h,
lib/same-inode.h, m4/afs.m4, m4/chdir-safer.m4.
The chdir-safer and afs files are now orphans; I'll remove them
unless someone speaks up.
Add lib/dirchownmod.c, lib/dirchownmod.h.
(Depends-on): Remove alloca, chown, save-cwd, dirname.
Add lchown, mkancesdirs.
(Maintainer): Add self.

* lib/dirchownmod.c, lib/dirchownmod.h:
* lib/mkancesdirs.c, lib/mkancesdirs.h: New files.
* lib/mkdir-p.c: Don't include alloca.h, stdio.h, sys/types.h,
unistd.h, string.h, chdir-safer.h, dirname.h, lchmod.h, lchown.h,
save-cwd.h.  Instead, include dirchownmod.h and mkancesdirs.h.
(make_dir_parents): New args MAKE_ANCESTOR, OPTIONS, ANNOUNCE,
MODE_BITS.  Remove options VERBOSE_FMT_STRING, CWD_ERRNO.  All
callers changed.  Revamp internals significantly, by not
attempting to create directories that are temporarily more
permissive than the final results.  Do not attempt to use
save_cwd/restore_cwd; it isn't worth it for mkdir and install.
This removes some race conditions, fixes some bugs, and simplifies
things.  Use new dirchownmod function to do owner and mode changes.
* lib/mkdir-p.h: Likewise.
* lib/modechange.c (octal_to_mode): New function.
(struct mode_change): New member mentioned.
(make_node_op_equals): New arg mentioned.  All callers changed.
(mode_compile): Keep track of which mode bits the user has explicitly
mentioned.
(mode_adjust): New arg DIR, so that we implement the X op correctly.
New arg PMODE_BITS, to keep track of which mode bits the user
mentioned; it treats S_ISUID and S_ISGID speciall.
All callers changed.
* lib/modechange.h: Likewise.

* mkancesdirs.m4: New file.
* mkdir-p.m4 (gl_MKDIR_PARENTS): Mention dirchownmod.c, dirchownmod.h.
Don't require AC_FUNC_ALLOCA, gl_AFS, gl_CHDIR_SAFER; no longer needed.
Require gl_FUNC_LCHOWN, since dirchownmod.c needs it.