68k: add delay on z80 rom access
68k: basic prefetch impl
68k: do not consume an int when the level doesn't change
helios: add gb emulation based on coffee-gb - not working too well atm
helios: add nes emulation based on the halfnes project
helios: backup sram, do not load empty files
helios: compute drift for more consistent framerates
helios: fix recent files handling
helios: load compressed roms
helios: mantain 4:3 aspect ratio by default
md: do not stop 68k on vdp fifo full, but only stop it if it tries to access vdp ports
md: fix dma fill when len=0
md: fm add dynamic rate control
md: improve shadow/highlight
md: use nuke Ym2612 emulation by default
md: savestates, use gsh format
md: support very small roms
sms: savestate fixes
ui: hide cursor on screen
ui: improve multi-screen support
ui: show info messages