This was becoming heavy to manage.

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.

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

Finally got rid of the XPACKed core and managed to cross-compile
all core words, which greatly simplifies the bootstrapping process.

TODO: implement X['] so that I can remove those XCURRENT patterns.

This leaves space for xcomp-core which is growing.

This allows us to move words like ABORT" to xcomp-core, which is
I think the last roadblock before being able to unify all drivers
into a single xcomp layer.

And refreshed description.

With all this recent movements, we had a bit of a fragmentation
issue.