Plug a leak that would cause rm or a cross-device mv to fail when

Plug a leak that would cause rm or a cross-device mv to fail when
operating on too many command-line-specified nonempty directories.

(remove_dir): Destroy the `struct saved_cwd' on the
top of the stack before returning.  This usually closes the file
descriptor that was used to return to the original working directory.
Reported by Cyril Bouthors in
http://article.gmane.org/gmane.comp.gnu.core-utils.bugs/3048