Autosave and news bugfixes

Three bugfixes, and a minor UI feature:

- Fixed bug where AUTO2.SAV was no longer being used; bug present since the save files were moved into a separate directory.
- Removed poorly functioning Windows-only legacy code. Applications should let the OS decide whether or not there is enough room on the filesystem, or else they might end up being their own denial-of-service cause, and things like user disk-quota are not taken into account anyway, so it's on the whole completely unreliable. Also, this code was not working fully because of the same bug as above.
- Minor feature: the savegames list now sorts the AUTO.SAV and AUTO2.SAV to the top of the list, such that these can easily be found.
- Fixed the issue with news messages disappearing when new news comes in, when news filter is set to Major news.
- Fixed bug where the last touched savegame was not being remembered by the savegame list, between runs.