This will facilitate the development of a solution for
cross-compiling directly to EEPROM.

So far, only the first 400 sectors of the disk image are accessible.

TODO: add keybindings to swap floppies on the emulated machine.

Not complete yet, but has @KEY and @DSP, enough to get prompt.

I'm planning on supporting Text Mode soon, and SMS' VDP, when mode
4 is not active, behaves mostly like a regular TMS9918.

By having this behavior in a separate unit, we'll be able to use it
in other systems.

NetBSD doesn't have ncurses. Linking to curses doesn't seem to change
anything. Tried on OpenBSD and Ubuntu.

Theoretically, it works. I can access an emulated SD card on it.

Will it work on real hardware?

I've also made SMS emulation faster. It was unbearably slow for SDC
access.

My idea of plugging a RC2014 bridge directly onto a Sega Master System
cartridge doesn't work. The SMS eats all I/O addr space, we can't use
it. Therefore, this naive idea, in the emulator, of reusing sdc.c in
sms.c as-is, doesn't work either.

I'll have to find another way of communicating to a SPI device on the
SMS. I'll probably do it through a controller port. Meanwhile, I need
to decouple SPI from SDC in the emulator code so that I can reuse
sdc.c. This is what is done here.

It works (in emulation, but soon on real hardware!), but the LIST
command is awkward due to tight screen estate...

I'm about to reuse sdc.c in sms.c and the old directory structure
was becoming awkward.

I'm planning on adding other subfolders. 8086 for example...

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

"-ansi" is not supported by tcc, but according to gcc
documentation, "-std=c89" produces identical behavior.

See: https://gcc.gnu.org/onlinedocs/gcc-3.4.2/gcc/Standards.html

Only its jump at 0x33 remains.

I've also fixed a strange offset oddity in 8086's (n) placement.
It was off by 2, but strangely, it ran properly. Anyway, now it's
fixed.

The C VM now runs the show.

All recipe makesfiles would previously assume a built emul/.

Fixes #113

Writing directly to forth.bin seems to cause problems in some
environments such as Travis CI.

Read the contents of forth.bin at runtime. This allows us to get
rid of the bin2c tooling.

Instead, embed absolute path to blkfs. Having to rebuild the stage
binary at every change in blkfs is getting tedious.

It doesn't change anything featurewise, but this change is in
preparation for the addition of an eventual AT-XY.

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

The way is clear for complete stage1 bootstrapping on the RC2014
target!

It doesn't serve much purpose and takes up many precious bytes. And,
after all, parsed didn't do it either...

This allows us to remove forth/z80a.fs. Another big step towards
self-hosting!

Also, fix some PSP leaks related to LOAD.

It's not used

The former was only used in the peculiar context of "/emul". The
regular case is actually HERE pointing to RAMEND on boot.

Let's revisit the relinking approach, with LITA this time.
This reverts commit 6652125d47.

... instead of building boot.fs, and then z80c.fs/icore.fs in separate
passes. This strengten xcomp by making it support 2 completely separate
dicts (that is, the X dict is *not* connected to the system dict. The chain
now stops at EXIT def in boot.fs).

Memory mapping is a dead end too, solution has to be at a higher
level. xcomp is my new approach.

This was a dead end.

Not quite functional yet, but works in toy situations. The goal is to
concatenate RC2014's bootstrapped dict to the boot binary.