Savegame fails to load due to conflict between SpellState and MagicEffects

https://forum.openmw.org/viewtopic.php?f=8&t=4054

There is a conflict between the SpellState and MagicEffects deserialization routines due to badly designed format - both use subrecords with the same magic number: "EFID". The bug can occur after getting cured of corprus.

Can always be reproduced using the savegame provided in the forum thread.

(RM-3714 from redmine: created on 2017-01-06 by Miroslav Remák, )