I'm instrumenting the Tree-sitter branch to make sure there's no glaring
memory issues like leaks or undefined behavior.  I've found that the
function treesit_load_language leaks a few bytes each time a language is
loaded.

To fix the bug, I've simplified a bit the logic that loads the dynamic
library, to avoid the string duplication that was leaking, and removed a
loop that I think it's not really necessary (that'll save us a few CPU
cycles).

Please check that I've not made any crucial mistake, and feel free to
merge it if you think it's a good patch.

Thanks.