New module 'fstat'.

New module 'fstat'.

* lib/sys_stat.in.h (fstat): Declare only if GNULIB_FSTAT is set.
* lib/fstat.c: New file, based on a piece of lib/fchdir.c.
* lib/fchdir.c (rpl_fstat): Remove function.
* m4/fstat.m4: New file.
* m4/fchdir.m4 (gl_FUNC_FCHDIR): Don't set REPLACE_FSTAT.
* m4/sys_stat_h.m4 (gl_HEADER_SYS_STAT_H): Test whether fstat is
declared.
(gl_SYS_STAT_H_DEFAULTS): Initialize GNULIB_FSTAT.
* modules/sys_stat (Makefile.am): Substitute GNULIB_FSTAT.
* modules/fstat: New file.
* modules/sys_stat-tests (Depends-on): Remove fstat-tests.
* tests/test-sys_stat-c++.cc (fstat): Check only if GNULIB_TEST_FSTAT
is set.
* doc/posix-functions/fstat.texi: Mention the new module and the
problem on MSVC.
* NEWS: Mention the change.
* modules/acl (Depends-on): Add fstat.
* modules/chdir-safer (Depends-on): Likewise.
* modules/chown (Depends-on): Likewise.
* modules/copy-file (Depends-on): Likewise.
* modules/fchdir (Depends-on): Likewise.
* modules/fdopendir (Depends-on): Likewise.
* modules/fopen (Depends-on): Likewise.
* modules/fts (Depends-on): Likewise.
* modules/getcwd (Depends-on): Likewise.
* modules/isapipe (Depends-on): Likewise.
* modules/linkat (Depends-on): Likewise.
* modules/lseek (Depends-on): Likewise.
* modules/mkdir-p (Depends-on): Likewise.
* modules/open (Depends-on): Likewise.
* modules/openat (Depends-on): Likewise.
* modules/read-file (Depends-on): Likewise.
* modules/renameat (Depends-on): Likewise.
* modules/utimens (Depends-on): Likewise.