21.0407

68k: overclock support
helios: init SRAM with 0xFF, according to docs
helios: init RAM with random values
helios: async write to file, mitigate sporadic savestate corruption
helios: add savestate support for sg1000, coleco, msx
md: select between 3/6 buttons joypad
md: vdp debug fixes
md: improve SVP auto-detection
md: change vdp registers init values, according to docs
md: hint tweaks
md: backPlane color issue
md: further windowPlane fixes
md: sh tweak
md: add support for vdp left column blanking
md: fix fm stereo
md: partial support for exssf mapper
md: unused bits on Z80_BUSREQ read, z80 zreset tweak
md: fix on saving serialized data
md: limit z80 pc range to RAM space only
md: fix hscroll cell mode
msumd: add support for CUE based loop points (MD+ style)
msumd: support PLAY_OFFSET, volume
nes: update lib
tms: fix vdp vram size
z80: update lib