I wanted to make CVM's forth use the Grid subsystem, but doing so
would break the stage binary. Hence, this split.

libz80 doesn't move much anymore, there not much advantage to the
git module indirection.

The C VM now runs the show.

Verifying that forth.bin is stable is enough. Also, fix shebang.

To update LATEST offset more easily. Will be useful for recipes.

It's no longer required to use `gmake` under OpenBSD and shell scripts
no longer require bash.