add LXC and Kernel version to docker info in debug mode

    $> docker -D info
    Containers: 77
    Images: 55
    Debug mode (server): false
    Debug mode (client): true
    Fds: 8
    Goroutines: 12
    LXC Version: 0.7.5
    Kernel Version: 3.8.0-19-generic 
    WARNING: No swap limit support