long term fixes for serialization/rewind issues with certain games

[markwkidd]

Previous discussion:

• if Rewind is enabled, some games instantly crash when loaded mame2003-libretro#338
• Turn off 'Rewind' function by default otherwise lots of games won't boot #175

There are some short-term fixes for the Rewind crash, but the long term solutions involve understanding why the serialization routine in combination with Rewind crashes in only some situations.

On the MAME end, there may be clues in the history for specific drivers.

On the serialization implementation end, radius posits:

you could detect if it's rewinding by checking if it's serializing every frame I guess I bet the problem is serializing at the first few frames
make it return false in the first 10 secs or whtever
if that's the case try to find a decent workaround 😛
maybe check the data I guess the size or data are null when you call retro serialize on one of those games
in such a case
return false

[markwkidd]

@grant2258 made progress on this issue with #542