MiSTer FPGA core update roundup

Arcade: Inferno (Williams):
– Fix Aim+Fire in 2 Player (typo)

– UMB A000h as an option (Some games use this segment to detect the EGA video card)
– Fix overflow flag, co-working with @MicroCoreLabs (Landmark System Speed Test 6.0 now works)
– Fix 0xF6 opcodes in MCL86 microcode, by @MicroCoreLabs
– Fix Tandy palette for 320x200x4 (Marble MadnessAlleyCat, etc… now working new palette)
– Improved bus speed, by @kitune-san (Demo 8088MPH now works better)
– bugfix in MCL86 microcode, by @kitune-san (KEYB now works)
– Fixed bios writable signal, by @kitune-san