Shivers uses extra special hardcoded save files together with the normal
ones that are used to store slot names and spot descriptions. The scheme
is a bit odd, and since the names of the extra save files are hardcoded,
this scheme is problematic to use. We skip the creation of these files
altogether and use virtual files instead, which means that the
(broken) spot descriptions won't be visible next to each save
description. This isn't a major issue for now, and it's left as a future
TODO to implement this feature in a cleaner way, and not with extra save
files. This scheme fixes the slot descriptions in the loading screen.
Also, kCD(1) has been implemented, which fixes loading of the save
states themselves
Phantasmagoria's scripts keep polling for the existence of the savegame
index file and request to read and write it using the same parameters
when opening it. The index file is closed and reopened for every save
slot, which is slow and can be much slower on non-desktop devices.
Also, the game scripts request seeking in writable streams and request
to expand the existing index file.
To provide this functionality and to reduce constant slow file opening
and closing, this virtual class has been introduced
