vsg::getDirectoryContents is broken on Windows

[appcodegen]

On the Windows platform this function simply does not do anything; to me it feels like someone just copied an API call and then only made sure it compiled ;)

Right now, the FindFirstFileNameW/FindNextFileNameW function pair is used, but with invalid parameters (required in/out parameters are simply set to nullptr). Note that I think these are actually the wrong functions, since these enumerate hard links only.

I think that actually the FindFirstFileW/FindNextFileW functions should be used.

I have a change here, I will see about creating a PR for this one

[robertosfield]

I had to implement it blind as I have only Linux systems here. I used the OpenSceneGraph implementation as starting place and got it compiling but have to rely upon the Windows community to help test/debug. I'd appreciate a PR fixing the problems.