bug#31138: Native json slower than json.el

[Eli Zaretskii]

> From: Dmitry Gutov <dgutov@yandex.ru>
> Cc: sebastien@chapu.is, yyoncho@gmail.com, 31138@debbugs.gnu.org
> Date: Mon, 22 Apr 2019 14:36:02 +0300
> 
> On 22.04.2019 1:12, Dmitry Gutov wrote:
> > Considering libjansson manages to do both JSON parsing and string 
> > conversion in ~the same time make_specified_string only does string 
> > conversion on the returned strings, it most likely follows that 
> > make_specified_string could be made faster.
> 
> ^ Sorry, I meant code_convert_string here.

That one is called both for encoding the input and for decoding the
strings in the result of parsing.