libffado: 2.3.0 -> 2.4.0 (maintenance)

http://ffado.org/?q=node/3379
This fixes build with gcc7.  The removed patches are inside now.

pkgs/os-specific/linux/ffado/default.nix

@@ -25,11 +25,11 @@ let
 in
 stdenv.mkDerivation rec {
   name = "${prefix}ffado-${version}";
-  version = "2.3.0";
+  version = "2.4.0";
 
   src = fetchurl {
     url = "http://www.ffado.org/files/libffado-${version}.tgz";
-    sha256 = "122z8gya60nyg47i738z2yr4qcjyk2xix4kwhf5ybkmp23kcgqqq";
+    sha256 = "14rprlcd0gpvg9kljh0zzjzd2rc9hbqqpjidshxxjvvfh4r00f4f";
   };
 
   nativeBuildInputs = [ scons pkgconfig which makeWrapper python ];
@@ -41,12 +41,8 @@ stdenv.mkDerivation rec {
     optXdg_utils libxmlxx glibmm
   ];
 
-  patches = [
-    ./gcc6.patch
-    ./glibc226.patch
-  ];
-
   postPatch = ''
+    sed '1iimport sys' -i SConstruct
     # SConstruct checks cpuinfo and an objdump of /bin/mount to determine the appropriate arch
     # Let's just skip this and tell it which to build
     sed '/def is_userspace_32bit(cpuinfo):/a\