kernel: enable AppArmor by default

AppArmor only requires a few patches to the 3.2 and 3.4 kernels in order
to work properly (with the minor catch grsecurity -stable includes the
3.2 patches.) This adds them to the kernel builds by default, removes
features.apparmor (since it's always true) and makes it the default MAC
system.

Signed-off-by: Austin Seipp <aseipp@pobox.com>

pkgs/os-specific/linux/kernel/common-config.nix

@@ -177,6 +177,10 @@ with stdenv.lib;
     USER_NS y # Support for user namespaces
   ''}
 
+  # AppArmor support
+  SECURITY_APPARMOR y
+  DEFAULT_SECURITY_APPARMOR y
+
   # Misc. options.
   8139TOO_8129 y
   8139TOO_PIO n # PIO is slower