This patch adds a "features.aufs2_1" to the aufs-2.1 patch for Linux
2.6.37 to prevent aufs2_1 and aufs2_1_util from being options for
kernels without an aufs 2.1 patch. There were several Hydra build
failures as a result of attempting to build aufs2.1 against older
kernels.
svn path=/nixpkgs/trunk/; revision=26597