implement hooks for cheat/rumble system and also hooks for save state/rewind

[RetroSven]

No description provided.

[vadosnaprimer]

You might be interested in my initial attempt to buffer states too, attached in this post:
mamedev#2398 (comment)

[RetroSven]

Hi @vadosnaprimer
I did see the ram state code, but it would have required reworking it to pass in any buffer to avoid a three way memcpy (origin -> ram state buffer -> RA buffer). I had already coded this for the mame2016 RA branch, so it was much simpler to just pop it in because I knew it already worked.
Thanks

[inactive123]

Will be pretty great to finally have serialization working in the current MAME core.