Implement SSF2 mapper for PicoDrive32x for homebrew games

[getCursorsExe]

It is possible to have a 32x homebrew game use SSF2 mapper. As a result, it is impossible to load these games in BizHawk, as PicoDrive32x doesn't support it at all, even when we change ROM header to the one from Super Street Fighter 2. This is normally used to expand ROM on Sega Genesis, but it can be done on 32x and Sega CD too, since they are extensions to Genesis.

[getCursorsExe]

Perhaps we should implement this to Sega Genesis emulation first (although it's likely a placeholder, removing the Sega Mega drive emulation from PicoDrive32x would make the core unusable), this might help in the future.