[RFC] Replace vim_strncpy with strlcpy

> but I think it's a good idea to try and keep this organized since working with strings is already a pain and at risk to cause bugs.

You couldn't be more right, this stuff is very finicky, since the function contracts differ in subtle ways. Let's keep the PRs as atomic as we can :). The only thing I think everyone can agree on is: it would be really really awesome if we could somehow detect if/when vim is relying on the zero-fill behaviour. Up until now I haven't thought of anything yet, but I have this feeling that it must be possible, somehow.