systemd: Update to 201

Fixes NixOS/nixos#135 and NixOS/nixos#126.

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

@@ -6,11 +6,11 @@
 assert stdenv.gcc.libc or null != null;
 
 stdenv.mkDerivation rec {
-  name = "systemd-200";
+  name = "systemd-201";
 
   src = fetchurl {
     url = "http://www.freedesktop.org/software/systemd/${name}.tar.xz";
-    sha256 = "05y2r25441nznif5xi5gab4c6xdywiqzgcl3nsmg0j2wzalbl24s";
+    sha256 = "046cr1q7xv7bslzc16g8zz8nddf64lw8v01isw1204n21cd9yafn";
   };
 
   patches =
@@ -21,6 +21,7 @@ stdenv.mkDerivation rec {
       ./0005-sysinit.target-Drop-the-dependency-on-local-fs.targe.patch
       ./0006-Don-t-call-plymouth-quit.patch
       ./0007-Ignore-IPv6-link-local-addresses.patch
+      ./0008-Don-t-try-to-unmount-nix-or-nix-store.patch
     ] ++ stdenv.lib.optional stdenv.isArm ./libc-bug-accept4-arm.patch;
 
   buildInputs =
@@ -68,11 +69,17 @@ stdenv.mkDerivation rec {
   NIX_CFLAGS_COMPILE =
     [ # Can't say ${polkit}/bin/pkttyagent here because that would
       # lead to a cyclic dependency.
-      "-UPOLKIT_AGENT_BINARY_PATH -DPOLKIT_AGENT_BINARY_PATH=\"/run/current-system/sw/bin/pkttyagent\""
+      "-UPOLKIT_AGENT_BINARY_PATH" "-DPOLKIT_AGENT_BINARY_PATH=\"/run/current-system/sw/bin/pkttyagent\""
       "-fno-stack-protector"
+
       # Work around our kernel headers being too old.  FIXME: remove
       # this after the next stdenv update.
       "-DFS_NOCOW_FL=0x00800000"
+
+      # Set the release_agent on /sys/fs/cgroup/systemd to the
+      # currently running systemd (/run/current-system/systemd) so
+      # that we don't use an obsolete/garbage-collected release agent.
+      "-USYSTEMD_CGROUP_AGENT_PATH" "-DSYSTEMD_CGROUP_AGENT_PATH=\"/run/current-system/systemd/lib/systemd/systemd-cgroups-agent\""
     ];
 
   # Use /var/lib/udev rather than /etc/udev for the generated hardware