niven on its way to x64 support

Before writing the renderer, I thought it might be a good chance to clean up the current build system and introduce x64 support. So far, only the external libs work (UnitTest++ and TinyXML). I hope to get a chance today to update the five niven libraries and two executables today. As soon as Boost 1.34 gets out (which is supposed to be supported on x64) I’ll probably switch one of my dev platforms completely over to x64.