bug#36447: 27.0.50; New "Unknown keyword" errors

[Eli Zaretskii]

> From: Pip Cet <pipcet@gmail.com>
> Date: Fri, 5 Jul 2019 18:57:56 +0000
> Cc: Eli Zaretskii <eliz@gnu.org>, michael_heerdegen@web.de, 
> npostavs@gmail.com, 
>       36447@debbugs.gnu.org
> 
> > His patch can/should be made slightly more efficient by only doing the
> > Fcopy_sequence on those hash-tables that are in purespace.
> 
> How do we test for that?

Can pdumper_object_p help?