bug#41946: 27.0.91; native json parsing: add :empty-object configuration

[Eli Zaretskii]

> From: Ivan Yonchovski <yyoncho@gmail.com>
> Date: Fri, 19 Jun 2020 08:52:57 +0300
> 
> 
> This is similar to :null-object/:false-object flags in
> json-parse-string and solves the same issue - inability to distinguish
> json's null from {}.

I don't think I understand the request.  Can you post more details,
please?  (Maybe it's some standard JSON feature that I'm not familiar
with?)