Added support for various disk formats used with HP computers. Named
'hp300', but also contains formats used with HP85 and HP150 computers,
using the same floppy drivers as the 300 series.
Most of the information was taken from "HP Flexible Disk Formats" by
Martin Hepperle.
HP LIF was used in quite a lot of different HP products like the
HP 9000/300, HP85/87 and HP150 computers. Added support for
reading this filesystem.
* bus/hp9845_io: Added HP9871 printer.
New working machines
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Hewlett-Packard HP 9825A
Hewlett-Packard HP 9831A
New working software list items
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hp9825_rom: 9862 Plotter/Gen I/O ROM for 9825
hp9825_rom: General/extended I/O ROM for 9825
hp9825_rom: General/extended I/O/9862 plotter ROM for 9825
hp9825_rom: General/extended I/O/plotter ROM for 9825
hp9825_rom: Plotter/Gen I/O ROM for 9825
hp9825_rom: String/Advanced programming ROM for 9825
hp9831_rom: Mass storage ROM for 9831
New not working software list items
------------------
hp9831_rom: Matrix/plotter ROM for 9831
* Marked double-sided images for single-sided releases as bad dumps.
* Added notes and serial numbers.
* Added ‘disk conversion’ to the descriptions of disk conversions.
* Removed disk conversions for software present in original form in other software lists.
* Removed non-working images made single-sided by cutting a double-sided dump in half: msxdosb, burgkilla, spacewlk, ballblaza, diamine2a, mj05, phstripa, raththaa, safarixa.
* Renamed spacewlka to spacewlk, mj05a to mj05, and pm1_asia to pm2_asia.
* Marked Spectravideo SVI-738 fully supported.
* Removed initial PCG bitmap fills these are always fully filled by later code.
* Use default PCG palette colour directly instead of pre-filling PCG bitmap.
* Combined per-pixel branches of logic based on "blend gfx with PCG/Text layers".
* nec/pc6001.cpp: Converted joystick ports to slots.
* nec/pc8801.cpp, nec/pc88va.cpp: Converted mouse port to a slot. Mouse
works beautifully in Ishido now, no jumpy movement.
