mesa: create a buildEnv that joins mesa (without glu) and glu

Since mesa-9.x, upstream has separated mesa and glu. @peti suggested using
buildEnv to create a mesa environment that acts like old mesa, which is what
this commit does.

pkgs/development/libraries/mesa/default.nix

@@ -12,7 +12,7 @@ let
   version = "9.1.1";
 in
 stdenv.mkDerivation {
-  name = "mesa-${version}";
+  name = "mesa-noglu-${version}";
 
   src = fetchurl {
     url = "ftp://ftp.freedesktop.org/pub/mesa/${version}/MesaLib-${version}.tar.bz2";