ZX Spectrum, ZX Next, TSConf, ZX81, PET2001

- Updated framework (adaptive scanlines, shadow mask, 64-phase filters).

- TSConf: Fixed a bug. High sprites were hidden (Ramon Martinez).

- ZXNext, TSConf: persistent image mounting (remembered across boots). Please rename boot.vhd(boot0.vhd, boot1.vhd) to other name if you want this feature working.