With this change we now once again can read pre 2.6 savegames.
Similarly savegames created after this fix will be readable by
ScummVM < 2.6.0. We will also be able to load savegames created
by ScummVM 2.6.x.
The only limitation is that since we now create the same kind
of savegames as older versions again, ScummVM 2.6.x will be
unable to load savegames created after this.
This fixes bug #13897
(cherry picked from commit 366c1e505d)