add the aufs3-loopback patch, and update to latest 3.15.10 kernel

this seems to stop #425 from happening for me.

and may well help with https://github.com/docker/docker/issues/7341.
So, since we're basically just taking a naked kernel and applying a subset of the AUFS patches to it, why don't we just switch to using the pre-patched AUFS source trees?  I can have a PR for this pretty quick (I've played with it before, but it was when I had less time to play here so I abandoned it).  Essentially, then we'd just set `CONFIG_AUFS_FS=y` in our kernel config and call it a day.

http://sourceforge.net/p/aufs/aufs3-linux/ci/aufs3.15/tree/
http://sourceforge.net/p/aufs/aufs3-linux/ci/aufs3.16/tree/

The biggest benefit of this would be that we know the full set of required patches are properly pre-applied and known to be working with that particular kernel version.