Move stat.h-substitute stuff from lib/stat-macros.h to lib/stat_.h.

Move stat.h-substitute stuff from lib/stat-macros.h to lib/stat_.h.
stat-macros.h is now for our own macros, whereas stat_h is for
macros in the <sys/stat.h> name space.
* lib/stat-macros.h: Remove copyright notice, as this file is now tiny.
(STAT_MACROS_H): Remove.
(S_IFMT, S_ISBLK, S_ISCHR, S_ISDIR, S_ISFIFO, S_ISLNK, S_ISNAM):
(S_ISMPB, S_ISMPC, S_ISNWK, S_ISREG, S_ISSOCK, S_ISDOOR, S_ISPORT):
(S_TYPEISMQ, S_TYPEISTMO, S_TYPEISSEM, S_TYPEISSHM, S_ISCTG, S_ISOFD):
(S_ISOFL, S_ISWHT, S_ISUID, S_ISGID, S_ISVTX, S_IRUSR, S_IRGRP):
(S_IROTH, S_IWUSR, S_IWGRP, S_IWOTH, S_IXUSR, S_IXGRP, S_IXOTH):
(S_IRWXU, S_IRWXG, S_IRWXO, S_IXUGO, S_IRWXUGO):
Move these macros to ...
* lib/stat_.h: here.  Don't include stat-macros.h.
* lib/canonicalize.c: Don't include stat-macros.h.
* lib/chown.c: Likewise.
* lib/euidaccess.c: Likewise.
* lib/file-type.c: Likewise.
* lib/filemode.c: Likewise.
* lib/glob.c: Likewise.
* lib/isapipe.c: Likewise.
* lib/lchown.c: Likewise.
* lib/lstat.c: Likewise.
* lib/mkdir-p.c: Likewise.
* lib/rmdir.c: Likewise.
* m4/lchown.m4 (gl_FUNC_LCHOWN): Don't require gl_STAT_MACROS.
* m4/sys_stat_h.m4 (gl_HEADER_SYS_STAT_H): Don't check for io.h
unless mkdir isn't declared, to speed up 'configure'.
Always create sys/stat.h, since it's unlikely any real sys/stat.h
would define all the S_* symbols.
* modules/canonicalize (Depends-on):
Depend on sys_stat, not stat-macros.
* modules/chown: Likewise.
* modules/euidaccess: Likewise.
* modules/filemode: Likewise.
* modules/file-type: Likewise.
* modules/glob: Likewise.
* modules/isapipe: Likewise.
* modules/lchown: Likewise.
* modules/lstat: Likewise.
* modules/mkancesdirs: Likewise.
* modules/rmdir: Likewise.
* modules/mkdir-p (Depends-on): Also depend on sys_stat.
* modules/modechange: Likewise.
* modules/stat-macros (Files): Remove m4/stat-macros.m4.
(configure.ac): Remove gl_STAT_MACROS.
* modules/sys_stat (Depends-on): Remove stat-macros.