Merge branch 'devel-2.6' into submit

* devel-2.6:
  Fix compatibility with newer Haskell libraries
  Fix gnt-instance console with xl

Conflicts:
        Makefile.am (reordering, fixed)
        htools/Ganeti/Confd/Server.hs (hlint fixes on master)
        htools/Ganeti/Daemon.hs (hlint)
        htools/Ganeti/HTools/Backend/Rapi.hs (hlint)
        htools/Ganeti/HTools/ExtLoader.hs (hlint)
        htools/Ganeti/HTools/QC.hs (file renamed/split in master, fixed)
        htools/test.hs (we don't use maxDiscards, ignored)
        lib/constants.py (move to pathutils)
        lib/hypervisor/hv_xen.py (move to pathutils)

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>