DSFix 2.5

Unofficial release not supported by PeterTh/Durante.

This build is meant as a testing bed for several improvements made after the official 2.4 release.

It includes fixes for: texture caching, alt+tabbing memory leak issues, water shader quality, (partial fix) sun not appearing under certain circumstances, savegame backups not working, etc. Files were also updated for VS 2017.

Thanks to prototype99 for the help (and further fixes).