added an option to disable background "overlay"
changed background image when background is 'pure black'
improved some menu transitions
minor menu arrangement & code cleanup
* improved sprites processing accuracy.
* fixed VBLANK transition line checks.
* code cleanup and (minor) optimizations.
[Core/Sound]
* increased FM internal sample size to 32-bit to avoid overflow when adding channels.
* added preliminary emulation of YM2612 DAC precision (can be configured to match real console output).
* added configurable roll-off for FIR filtering in High-Quality FM mode.
[Wii]
*added support to enable/disable Video Encoder Trap Filter: can help reproducing "color blending" as on a real Genesis (composite video only).
*added support to configure Video Encoder gamma correction.
~improved messagebox when loading ROM files with SRAM/Savestate "autoload"
~modified messageboxes titles & some error messages
~improved ROM file selection with the wiimote
~fixed VDP horizontal mode when loading savestate
~modified horizonatl scaling in Original mode.
~compiled with SVN libfat (read-ahead cache is now automatically used)
