* NEWS: Document that mkdir -p and install -d now fork on occasion.

* NEWS: Document that mkdir -p and install -d now fork on occasion.
* bootstrap.conf (gnulib_modules): Add savewd.
* src/install.c: Include savewd.h.
(process_dir): New function.
(main, install_file_in_file_parents): Use it, along with the new
savewd module, to avoid some race conditions.
* src/mkdir.c: Include savewd.h.
(struct mkdir_options): New members make_ancestor_function, mode,
mode_bits.
(make_ancestor): Return 1 if the resulting directory is not readable.
(process_dir): New function.
(main): Use it, along with new savewd module, to avoid some
race conditions.  Fill in new slots of struct mkdir_options, so
that callees get the values.
* tests/install/basic-1: Test for coreutils 5.97 bug that was
fixed in coreutils 6.0, and which should still be fixed with
this change.
* tests/mkdir/p-3: Likewise.