20260711

• More performance work - frontend improvements and hardwired fast paths for common instructions.
• Doom timedemo performance improves to 27.3 FPS, +30% compared with 21.0 FPS on ao486.

Known issues: intro artifacts in King's Quest IV and hang in Tyrian.

Put MiSTer in /media/fat, z386_*.rbf in /media/fat/_Computer, and boot0.rom, boot1.rom and disk images in /media/fat/games/Z386.