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

XPACKed source needing to be kept in bootstrap bin didn't make
much sense. With the removal of stripfc, it makes more sense to keep
the compiled form of stage 1 in repository as a bootstrap binary.

Also, rename it to forth.bin.

Big bootstrapping change which greatly reduces the role of the modern
operating system in the bootstrapping process.

This will allow us to read from blkfs in tests.

Less noisy this way

as well as emulator support for it. We can now write an edited
block back to "blkfs".

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

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.

This requires us to significantly adjust our build process, which
now has 3 stages.

Modest first step

Big one.

This allows us to write higher order words directly in Forth, which is much
more convenient than writing post-immediate (see "NOT" structure in diff if
you want to see what I mean) structures in ASM.

These structures can then be written to ROM (rather than loaded in RAM for
definitions loaded at run-time).

That's quite a bit of tooling that was added, 2 compilations stages, but I
think it's well worth it.