Fix 64-bit Windows support

[pmachapman]

The 64-bit build is buggy and broken for Visual Studio on Windows.

[sskras]

Is this not fixed yet? Asking per 82aaa87#diff-874e1ab6231f76437898785747235e071c862a8d48ce8244634c4109a872962bR16 :)

[pmachapman]

No, I haven't looked at the bugs on x64. I only added the build, realised it was broken, then created this issue. The 32-bit build is fine AFAIK.