Update to latest HEAD.
    
    - Add simple way to specify a group of pkgs. for version. BZ 913461.
    - Change group install => group upgrade for installed groups. BZ 833087.
    - Give more text when telling user about y-c-t, mention history. BZ 974576.
    - Fix the tolerant yum.conf text.
    - Skip installonly limit, if something has set check_future_rpmdbv. BZ 962757.