Their asm code has been broken for a little while! oops!

Also, fix the SPI relay driver to properly AND-away the result of
the CTL read.

Tested with a real prototype, works fine.

By default, it changes nothing, but it allows interesting
setups, such as using AT28! for directly uploading to EEPROM.

I've also updated the EEPROM recipe to upload directly to 0x2000.
I'm not sure what has changed, but it's working fine now.

Working on programming AVR chips exposes a glaring omission in my
first design of the SPI Relay: not allowing multiple devices make
this task hard. I constantly have to unplug my SD card before, plug
the AVR chip holder, then play a bit, then unplug the AVR holder,
then replug the SD card...

My prototype for a SPI relay design is built, but I haven't tested
it yet. I need to adapt the code first, which is what I do here.

When the prototype is tested, I'll update the SDC recipe with a new
schema.

AVR chips often run at less than z80's system clock. This means that
our SPI relay needs to have its own clock to properly communicate
with it. This means that the delay between OUT and IN can't be
hardcoded to 2 NOPs anymore. It needs to be configurable.

Although the SPI Relay driver is RC2014-specific, the SD Card driver
is generic enough to be a subsystem. That's the second subsystem we
add and this warrants, I think, the formalization of a new concept:
protocols.

Previously, it could never write more than a few bytes before pingpong
getting a mismatch error. Now, I can pingpong Collapse OS binary
without a mismatch.

My intention is to reuse the SPI relay to program AVR MCUs from a
RC2014.

It's more descriptive this way. Also, I'll soon add a new HERESTART
config.

Previously, recipes that began spitting binary contents before
loading block 282 would end up with VARIABLE code in their binary,
thus breaking them. We fix this by making this loading process
2-part.

Much faster!

ref #82

VE works! well, at this point, we can say that Collapse OS runs on
PC/AT. A little cleanup and docs writing and we're done!

On real hardware, there aren't always 2 heads...

instead of hardcoded drive 0.

That INT 13H logic was a bit tricky to implement...

read-only for now.

Also, fix (roll) which wasn't properly implemented.

Forth intepreter now works! There's still DOES> and overflow checks
to implement, but otherwise, we have it!

Not working, but we do get that sweet "CollapseOS".

almost there!

This port is taking shape!

8086 asm is a lot terser than z80... Those indirect memory operations
are very handy.