Add simple scrolling in floppy swap list in FS-UAE

[FrodeSolheim]

[saladinalep]

I don't know how difficult this would be to implement. I might be up to it. My interest in scrolling is for the save state menu. It would be great to extend the number of save slots beyond 9, don't you think? The bottom-most entry would be "Create new save", so there would be no need for a hard-coded limit.