Bunch of improvements in the device, memory and MMU handling.
Re-worked the NEAT 286 chipset (ported from VARCem).
Re-worked the ATI 28800 a bit, added Sierra SC1502x ramdac to VGA Wonder XL (Compaq) since it supports such.
Top 384K memory handling improvements (256K top memory too)
Added MCA version of MPU-401 (not tested much, however).
Re-worked the SCAT 286 chipset.
Fixes to various hard disk controllers;
Added the Packard Bell PB640;
Fixed the InPort mouse emulation - now it works correctly on Windows NT 3.1;
Removed the status window and the associated variables;
Completely removed the Green B 486 machine;
Fixed the MDSI Genius;
Fixed the single-sided 5.25" floppy drive;
Ported a CPU-related commit from VARCem.
IBM.H is gone, video stuff re-organized. Keyboard stuff reorganized.
Machines that have their own video, mouse and/or keyboard now have all this in their machine file.
Fixed and other cleanups here and there.
