Fix OS detection on Windows 10.
Compatibility mode will be handled in a later diff.
Comments by: @Itms, @vladislavbelov
Differential Revision: https://code.wildfiregames.com/D2420
#3299
It's not a really good initialization. System and complex structs should be initialized explicitly.
I went for the original code style. Can (and will!) be fixed in D3135. I still need your input for that one :)