bug#58823: feature/tree-sitter doesn't build without tree-sitter

[Eli Zaretskii]

> Cc: 58823@debbugs.gnu.org
> From: Yuan Fu <casouri@gmail.com>
> Date: Thu, 27 Oct 2022 15:59:14 -0700
> 
> > On Oct 27, 2022, at 2:01 PM, Stefan Kangas <stefankangas@gmail.com> wrote:
> > 
> > This system does not have tree-sitter installed.  The
> > feature/tree-sitter branch doesn't seem to build without it.
> 
> Oh, right, the lisp code has to prepare for the case where tree-sitter is not 
> compiled. Should we declare-function for all the functions in treesit.c?

Yes.

> And all tree-sitter code called by other lisp files should be guarded by 
> treesit-available-p. I can fix that.

Yes, thanks.