bug#66732: tree-sitter fontification doesn't update multi-line syntax reliably

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Eli Zaretskii <eliz@gnu.org>,  66732@debbugs.gnu.org,
>   dominik@honnef.co,  Yuan Fu <casouri@gmail.com>
> Date: Mon, 18 Dec 2023 14:12:02 -0500
> 
> I'm surprised that 42 behaves differently from t.

The display code in C tests only for nil or non-nil, but jit-lock.el
tests against a literal t in a few places.  (And don't forget about
the special value 'defer' we use.)

> What we really need here is to force the redisplay to consider that this
> part of the buffer needs to be re-rendered.

AFAIU, it will only re-render that part of some of the faces changed.