Modified VS project to support out of tree builds.
Modified VS project to support out of tree builds.

mwgoldsmith/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx