[hatari-devel] Improve memory snapshot consistency when doing save/restore

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Hello

similar to the recent changes to handle quit/reset/cpu setting in the 
same way as WinUAE does (ie at the end of the current instruction), I 
also modified saving/restoring snapshot to work the same.

This should greatly improved the (rare) cases where some games/demos had 
bad results (or even crash) after a restore (as reported for example by 
Vincent Riviere on Lethal Xcess).

I also fixed a few corner cases regarding some video variables and 
internal interrupt variables, so hopefully restoring a memory snapshot 
should now continue exactly from the same point the saving was done.

Nicolas