Hash and detect savedata hashmode correctly

Fixes Persona 1 savedata compatibility (bidirectional.)  I have not tested this in a ton of other games, it probably could use more testing.

Important: this does load old savedata, but once you save it'll be saved the new PSP compatible way.  It won't load in older versions of PPSSPP anymore, just like real PSP savedata didn't.  A warning is shown to the user that this will happen when the savedata is loaded.

This does not help Gods Eater Burst which has a different class of issue.  However, it's likely to help any game that had trouble with savedata transferring between a PSP and PPSSPP in a game that was created after sdk 2.70.

-[Unknown]