Windows x64 support

[martindevans]

Currently the DLL loader on windows does not load the 64 bit dependencies when loaded into a 64 bit process.

This code always throws when the process is compiled as x64:

var ptr = LoadLibrary(path);
if (ptr == IntPtr.Zero)
    throw new DllNotFoundException(string.Format("Failed to load DLL '{0}'. See https://github.com/martindevans/SupersonicSound#installation-instructions", path));

Even when it is being pointed at 64 bit DLLs. Loader has been modified to throw a NotImplementedException when loaded in a 64 bit process until this is resolved.

[martindevans]

This is probably because the "WIN64" symbol which the primitive FMOD C# wrapper depends upon is never defined!

[christopherpross]

Hello,
I read a blog article, where the author discribe the problem, maybe it can help here?
https://mysteriousspace.com/2015/05/31/fmod-in-c-its-a-pain-to-set-up-heres-how-i-did-it/

It would be very nice, if I can use your wrapper also in 64 bit windows...

[galead]

ConsoleTest project runs perfectly and plays sounds under x64 if you make few minor changes:

1. Copy fmod64.dll and fmodstudio64.dll to the "Dependencies\x86_64" folder. I just modified CopyFromFModInstall.bat and used it.
2. Added WIN64 symbol to SupersonicSound project settings.
3. I set it up in the PlatformTarget project settings: AnyCPU, unchecked "Prefer 32-bit".
4. Commented out the line
   //throw new NotImplementedException("Loading DLLs for x64 not
   in Native.cs file.

[martindevans]

Nice! Would you like to make a Pull Request with these changes?