Build: transform util directory to libutil convenience library
    
    This is autoconf way of doing things. It should allow us to enable
    subdir-objects automake option and stay compatible with future versions
    of automake.
    
    https://fedorahosted.org/freeipa/ticket/6418
    
    Reviewed-By: Lukas Slebodnik <lslebodn@redhat.com>
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>