GXemul Code2

Beginning to convert the CHIP8 cpu in the CHIP8 machine to a
(more correct) RCA 180x cpu. (Disassembly for all 1802
instructions has been implemented, but no execution yet, and
no 1805 extended instructions.)

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Adding skeq and skne instruction implementations.

Various CHIP8 updates.

Implementing a CHIP8 cpu mode, and a corresponding CHIP8
machine, for fun. Disassembly support for all instructions,
and most of the common instructions have been implemented:
mvi, mov_imm, add_imm, jmp, rand, cls, sprite, skeq_imm, jsr,
skne_imm, bcd, rts, ldr, str, mov, or, and, xor, add, sub,
font, ssound, sdelay, gdelay, and bogus skup/skpr.
(No support for actual sound yet, and no keyboard stuff.)

Minor updates to the LCA PCI controller.

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Adding bogus SCSI commands 0x51 (SCSICDROM_READ_DISCINFO) and
0x52 (SCSICDROM_READ_TRACKINFO) to the SCSI emulation layer,
to allow NetBSD/pmax 4.0_BETA to be installed from CDROM.