add a new build system

Hello this is a WIP branch. It should fully working on linux and OS X. Was tested briefly with mingw and totally untested on other platforms for lack of willing people. If you run anything but OS X or linux I would appreciate very much testing and feedback.

The only part missing is the processing of mpv.rc with windres. I'd appreciate if someone can add a patch for this missing functionality. Apparently there is a waf Tool to do it, but it assumes windres is always present.