anchor.diff:  , libdrm, xorg, wayland, udev, llvm, libffi
   , libvdpau
   , enableTextureFloats ? false # Texture floats are patented, see docs/patents.txt
  -, enableR600LlvmCompiler ? false # we would need currently unreleased LLVM or patches
  +, enableR600LlvmCompiler ? false # current llvm-3.3 + mesa-9.1.6 don't configure
   , enableExtraFeatures ? false # add ~15 MB to mesa_drivers
   }:
   
  
positive.code: */
  
  let
    version = "9.1.4";
    driverLink = "/run/opengl-driver" + stdenv.lib.optionalString stdenv.isi686 "-32";
  in
  stdenv.mkDerivation {
  
negative.code: 
    src = fetchurl {
      url = "ftp://ftp.freedesktop.org/pub/mesa/${version}/MesaLib-${version}.tar.bz2";
      sha256 = "0gay00fy84hrnp25hpacz5cbvxrpvgg1d390vichmbdgmkqdycp6";
    };
  
    prePatch = "patchShebangs .";
  