Windows: Fix detection of Windows 10 when manifest declares support

Windows: Fix detection of Windows 10 when manifest declares support

On Windows 10 GetVersionEx will return version 10.0 when the running
application has a manifest that declares Windows 10 compatibility.

https://docs.microsoft.com/en-us/windows/win32/sbscs/application-manifests#supportedOS

When no such manifest is found, the call will report version 6.2,
which is Windows 8.

The 6.4 version is returned by early Windows 10 Insider Previews
and Windows Server 2017 Technical Preview 1.

Closes #604

Signed-off-by: Axel Gembe <derago@gmail.com>
Signed-off-by: Nathan Hjelm <hjelmn@google.com>