* NEWS: Mention this.
* bootstrap.conf (gnulib_modules): Add stdopen.
* doc/diffutils.texi (Comparing Directories):
Do not document behavior if stdin is closed.
* src/diff.c: Include stdopen.h.
(main): Call stdopen early.
(compare_files) [__hpux]: Remove recently-introduced
special case for HP-UX exec with stdin closed.
* tests/new-file: Remove tests of the removed feature.