Before this commit, `cp -a` would terminate with a non-zero status
code on Windows because there are no extended attributes (xattr) to
copy. However, the GNU documentation for cp states

> Try to preserve SELinux security context and extended attributes
> (xattr), but ignore any failure to do that and print no
> corresponding diagnostic.

so it seems reasonable to do nothing instead of exiting with an error
in this case.

Fix a bug where `cp` failed to copy ancestor directories when using
the `--parents` option. For example, before this commit:

    $ mkdir -p a/b/c d
    $ cp --parents a/b/c d
    $ find d
    d
    d/c

After this commit

    $ mkdir -p a/b/c d
    $ cp --parents a/b/c d
    $ find d
    d
    d/a
    d/a/b
    d/a/b/c

This commit also adds the correct messages for `--verbose` mode:

    $ cp -r --parents --verbose a/b/c d
    a -> d/a
    a/b -> d/a/b
    'a/b/c' -> 'd/a/b/c'

Fixes uutils#3332.