Gauntlet arcade board prototype

The board and TMS5220C implementation are adapted from the BSD-3-Clause
hardware descriptions, speech processing, coefficients and slapstic logic in
MAME. Corresponding upstream sources:
https://github.com/mamedev/mame/tree/f8f6b22c3f328b9e0b04ff502989f8536c0d66c0
src/mame/atari/gauntlet.cpp
src/mame/atari/atarimo.cpp
src/mame/atari/slapstic.cpp
src/devices/sound/tms5220.cpp
src/devices/sound/tms5110r.hxx
src/emu/emupal.h

Copyright holders: Aaron Giles, Frank Palazzolo, Jonathan Gevaryahu,
Raphael Nabet, Couriersud and Michael Zapf. The original MAME implementation
also acknowledges Atari Games for hardware information. Local adaptations
remove MAME's framework, use package-owned bounded buffers, predecode graphics,
and implement only the original Gauntlet board and TMS5220C SPEAK EXTERNAL path.
The decoder does not provide a complete TI-99/4A speech device or general MAME.

The SID pitch arrangement references the YM2151 phase-step table in ymfm,
Copyright (c) 2021 Aaron Giles, BSD-3-Clause:
https://github.com/aaronsgiles/ymfm/blob/master/src/ymfm_fm.ipp
It approximates YM2151/POKEY music and effects on three or six SID voices.
It does not reproduce FM operators, all POKEY modes, or the original synthesis.

Musashi, Copyright (c) 1998-2001 Karl Stenerud, MIT:
https://github.com/kstenerud/Musashi/tree/313ebf1bd9f4d0d93341eb5ce21fd8a119e9dbdd
Local configuration targets 68010 only, excludes FPU/MMU dependencies and
factors equivalent generated handlers with an external 16-bit decode map.
Original license text remains in vendor/musashi/readme.txt and source headers.

The sound CPU uses floooh/chips m6502, Copyright (c) 2018 Andre Weissflog,
zlib license, revision 9e88298ce56319953ac7a43213a1120359f7a3a6.
The unmodified header and license are in shared/cpu/chips-9e88298/.

The package reuses the maintained MPE Prism+ receiver and SIDKick Pico PCM8
transport. Their licenses remain in the accompanying source archive and
PRISM-LICENSE.txt. Supply corresponding source with any distributed build.

Original arcade ROMs, graphics and speech remain copyright their owners.
They are private inputs and are not included in the source repository/archive.
