This is the first commit I do entirely in VE. It's a habit I'm planning
on taking as it helps a lot to find usability issues.

The address returned in the error condition would be off by one.

I'm not sure why I chose null-terminated initially. Probably because
the z80asm version had null-terminated strings.

Length-prefixes strings are the traditional form of strings in Forth
and it's a bit easier to work with them with traditional forth words
when they're under this form.

and renamed it "Core words". Also, reworded the presentation.

I hadn't noticed that this word was almost ANS compliant.

This allows us to get rid of the (parse*) indirection.

The way is clear for complete stage1 bootstrapping on the RC2014
target!