[RFC] Replace vim_strncpy with strlcpy

I like this idea. That being said. I still have to convert strncpy and STRNCPY calls over to STRLCPY. So I think I'll work on those primarily, and then do what you're suggesting all at once. This is a little more work (or at least it seems more tedious) 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.

So I'll remove the last commit for now (assuming @philix agrees) and then am I good to set this to RDY?