Apply mornfall's SANE patches

Fix sane-backends to generate udev rules, add a snapshot of sane-backends's unstable repo, and add a SANE nixos module

svn path=/nixpkgs/trunk/; revision=30764

pkgs/misc/sane-backends/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, hotplugSupport ? false, libusb ? null
+{ stdenv, fetchurl, hotplugSupport ? true, libusb ? null
 , gt68xxFirmware ? null }:
 let
   firmware = gt68xxFirmware {inherit fetchurl;};
@@ -20,6 +20,7 @@ stdenv.mkDerivation {
   postInstall = ''
     if test "$udevSupport" = "1"; then
       ensureDir $out/etc/udev/rules.d/
+      ./tools/sane-desc -m udev > $out/etc/udev/rules.d/60-libsane.rules || \
       cp tools/udev/libsane.rules $out/etc/udev/rules.d/60-libsane.rules
     fi
   '';

pkgs/misc/sane-backends/snapshot.nix

@@ -0,0 +1,33 @@
+{ stdenv, fetchurl, hotplugSupport ? true, libusb ? null
+, gt68xxFirmware ? null }:
+let
+  firmware = gt68xxFirmware {inherit fetchurl;};
+in
+assert hotplugSupport -> stdenv.system == "i686-linux";
+
+stdenv.mkDerivation {
+  name = "sane-backends-1.0.22.git201111204";
+  
+  src = fetchurl {
+    url = http://www.sane-project.org/snapshots/sane-backends-git20111204.tar.gz;
+    sha256 = "00b3fi8zjrq3in0wndz1xcz228mgfhwhh2knmyjsikr88hal0m47";
+  };
+  
+  udevSupport = hotplugSupport;
+
+  buildInputs = if libusb != null then [libusb] else [];
+
+  postInstall = ''
+    if test "$udevSupport" = "1"; then
+      ensureDir $out/etc/udev/rules.d/
+      ./tools/sane-desc -m udev > $out/etc/udev/rules.d/60-libsane.rules || \
+      cp tools/udev/libsane.rules $out/etc/udev/rules.d/60-libsane.rules
+    fi
+  '';
+
+  preInstall =
+    if gt68xxFirmware != null then 
+      "mkdir -p \${out}/share/sane/gt68xx ; ln -s " + firmware.fw +
+      " \${out}/share/sane/gt68xx/" + firmware.name
+    else "";
+}

pkgs/top-level/all-packages.nix

@@ -8486,6 +8486,10 @@ let
     gt68xxFirmware = getConfig ["sane" "gt68xxFirmware"] null;
   };
 
+  saneBackendsSnapshot = callPackage ../misc/sane-backends/snapshot.nix {
+    gt68xxFirmware = getConfig ["sane" "gt68xxFirmware"] null;
+  };
+
   saneFrontends = callPackage ../misc/sane-front { };
 
   slock = callPackage ../misc/screensavers/slock { };