It was badly handled.

All "stop pings" are now explicitly made at appropriate places. This
fixes a problem I've introduced in the last commit where RAM+ was
unexpectedly part of a stable ABI because of "HERE" usage in dummy.fs.

This system will, anyways, soon change because boot.bin and z80c.bin
will be built during the same process (but there's a bit of retooling
to do before I get there).

Doing this was a bit stupid. These offsets are constants. Moreover,
having them in stable ABI had us construct the boot binary from the
stable ABI of the host, making it very difficult to change RAMSTART
for a new system.

This commit cuts Forth's dependency on zasm. It now self-assembles
its own boot-binary! Things are a bit messy now, I'll clean up
later.

Make LATEST configurable through a value in the binary instead of through
a ZASM constant. This enables the simple concatenation of compiled dicts and
simplifies the build process.

Not needed anymore. CONSTANT does the trick.

Now we're having a real nice and tidy forth.asm...

We refer to stable offset as direct numbers instead of offset to JTBL.
Simpler that way.

forth.asm under 1K lines!

inc (hl) is 8 bit, inc (hl) is 8 bit, inc (hl) is 8 bit. Now I hope
I'll remember...

There is an alternate git history where I continued the Forth-ification of
words, including "SKIP?", but that was a bad idea: because that word was
written by flow control immediates, I stepped into quicksands where stability
became necessary in z80c.fs and I couldn't gracefully get out of it.

I'm stepping back and take this opportunity to replace the shoddy SKIP? algo
with a more straightforward (?br) implementation.

(br) and (?br) will always stay in boot code where it's easier manage a stable
ABI.

I can't get rid of "(fbr)" and "(bbr)" just yet, but soon...