udev: complete rework

- systemd puts all into one output now (except for man),
  because I wasn't able to fix all systemd/udev refernces
  for NixOS to work well
- libudev is now by default *copied* into another path,
  which is what most packages will use as build input :-)
- pkgs.udev = [ libudev.out libudev.dev ]; because there are too many
  references that just put `udev` into build inputs (to rewrite them all),
  also this made "${udev}/foo" fail at *evaluation* time
  so it's easier to catch and change to something more specific

pkgs/development/libraries/libusb1/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, pkgconfig, udev ? null, libobjc, IOKit }:
+{ stdenv, fetchurl, pkgconfig, libudev ? null, libobjc, IOKit }:
 
 stdenv.mkDerivation rec {
   name = "libusb-1.0.19";
@@ -12,13 +12,13 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ pkgconfig ];
   propagatedBuildInputs =
-    stdenv.lib.optional stdenv.isLinux udev ++
+    stdenv.lib.optional stdenv.isLinux libudev ++
     stdenv.lib.optionals stdenv.isDarwin [ libobjc IOKit ];
 
   NIX_LDFLAGS = stdenv.lib.optionalString stdenv.isLinux "-lgcc_s";
 
   preFixup = stdenv.lib.optionalString stdenv.isLinux ''
-    sed 's,-ludev,-L${udev}/lib -ludev,' -i $out/lib/libusb-1.0.la
+    sed 's,-ludev,-L${libudev.out}/lib -ludev,' -i $out/lib/libusb-1.0.la
   '';
 
   meta = {