A small fix that isn't actually an issue in this MR, but will be with the proxy impl (it's an issue on my branch). In `dispex_prop_get` we now go recursively through PROTREFs, just like invoke, since prototypes can be other objects overriding dispex props (proxy objects with overrides). `dispex_prop_put` is the same since that's not needed there, and it also has special case only for accessors.