Improve libvlc.dll detection

[pjeanjean]

This doesn't actually fix #140 , but it should probably help users that are using a 32bits version of Python on Windows, and it should also help to debug future issues with the DLL detection function.

[kethan1]

No code change can fix #140 as that was caused because of using 64 bit python with 32 bit VLC.

[kethan1]

@oaubert any plans on merging this

[oaubert]

I was waiting for some feedback on my suggestion to merge this with #152 and provide more explicit error messages for the various error cases (which may also point to some FAQ). I was also thinking especially about the #140 use case (which is a very FAQ): ideally, if you can find the DLL file but cannot load it, it should display an error message giving the procedure to check the architecture for VLC (and display the arch for python). This needs to be done by a Windows developer.
But if you do not have the time, your current patch could be merged almost as-is (except that I would rather have only the header.py file modified, not the generated modules themselves).