Goal:
  
  G1 : t
  G2 : t
  eos : CoreTactics.end_of_section
  fix_0 : forall (s : VSet.t) (x y : V.t) (p : SPath G2 s x y),
          first_in_graph s x y p (first_in p)
  ============================
   (forall (s : VSet.t) (x y : V.t) (p : SPath G2 s x y),
    first_in_graph s x y p (first_in p))


DEBUG:Going to execute:
specialize_mutual