rm: use gnulib faccessat

* bootstrap.conf (gnulib_modules): Add faccessat.  Replace strdup
with strdup-posix.
* m4/jm-macros.m4 (coreutils_MACROS): Revert previous change, now
that gnulib does it for us.
* src/remove.c (write_protected_non_symlink): Use faccessat in
more situations.

bootstrap.conf

@@ -78,6 +78,7 @@ gnulib_modules="
   euidaccess
   exclude
   exitfail
+  faccessat
   fchdir
   fcntl
   fcntl-safer
@@ -197,7 +198,7 @@ gnulib_modules="
   stdlib-safer
   stpcpy
   stpncpy
-  strdup
+  strdup-posix
   strftime
   strpbrk
   strtoimax