Don’t CLONE nameless hashes

Don’t CLONE nameless hashes

The cloning code was trying to call CLONE on nameless hashes that nonetheless had an effective name (HvENAME).

This can happen if a nameless hash is assigned over a stash, as in

  *foo:: = {}

or if a stash is undefined:

  undef %foo::

(The effective name is how perl tracks the location internally, for
the sake of updating MRO caches.)