During "make updatebootstrap", we use less than 0x20 bytes on the
PSP side and less than 0x40 bytes on the RSP one. 0x100 bytes ought
to be enough for anybody.

Use straight VARIABLE instead of Z80MEM+. Initially, I used this
system to allow z80a to be embedded in a system binary, but now
I don't think it's worth it. Compiled, z80a is 2.5k. Sure, it's a
sizeable amount of RAM, but I think that even with it in RAM, I'll
manage a bootstrap within my most constrained machine, the SMS with
8K.

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

Saves us an (ok) indirection and will save us more soon.

This should allow me to simplify LOAD's exit mechanism on block
end.

My mind is getting forthy.

This allows me to reclaim some RAM I hadn't even noticed I
needlessly monopolise.

That INIT thing is unnecessary.

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

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.

DO and LOOP now only compile words from stable ABI, which make them
suitable for xcomp. This will greatly simplify driver writing and
allow us to mostly avoid the low/high divide in drivers.

LEAVE is still xcomp-incompatible though.

This make us very very tight for "<0x100" limit for literal words.
Hopefully, we won't need more stuff in that area of the binary...

This makes [entry] much simpler. Also, remove unused LITS word.

Now I struggle to remember why I ever did things they way I did.
There must have been a reason...

The goal is to insert device drivers in between.

That makes it easier to write drivers that can be xcompiled.

Also, made LIST properly handle full 64-chars lines not ending with
a null or CR. Previously, such a line would be accompanied by its
following line, duplicating that line's output.

This allows us to make DO..LOOP more compact.

This was caused by the removal of signed-ness a long while ago.

Lines edited with the Block editor end with 0xd and (print) spits
spurious CR when printing those lines.

Also, properly initialize ACC in BROWSE.

And use them in all places they make sense.

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

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

Not worth the complexity and space.

2 was overkill