finding relative loops

with the current implementation

    ; noh =
      [Forward,Backward,Forward_Backward,Overlap] >>= \ c ->
      [ Worker (Enumerate {closure=c
                          --  , tracing=True
                           } )
      ]

results are abysmal: we do find 1 loop only. MnM finds 8.

The hard loops are in Waldmann_19/random. These are length-preserving systems, so we could use some specialized method #389 . But the general method must work as well.